Acyloxyalkyl carbamate prodrugs, methods of synthesis and use

ABSTRACT

Acyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid and analogs thereof, methods of making acyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid and analogs thereof, methods of using acyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid and analogs thereof, and pharmaceutical compositions comprising acyloxyalkyl carbamate prodrugs 3-aminopropylphosphinic acid and analogs thereof for treating diseases or disorders such as mild cognitive impairment, cognitive impairment associated with Alzheimer&#39;s disease Alzheimer&#39;s disease, depression, anxiety, and epilepsy are disclosed. Acyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid and analogs thereof, which are suitable for oral administration and sustained release oral dosage forms are also disclosed.

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Application Ser. No. 60/844,640 filed Sep. 15, 2006, whichis incorporated by reference herein in its entirety.

FIELD

The disclosure relates to acyloxyalkyl carbamate prodrugs of3-aminopropylphosphinic acid and analogs thereof, methods of makingacyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid andanalogs thereof, methods of using acyloxyalkyl carbamate prodrugs of3-aminopropylphosphinic acid and analogs thereof, and pharmaceuticalcompositions comprising acyloxyalkyl carbamate prodrugs of3-aminopropylphosphinic acid and analogs thereof to treat disease. Thedisclosure also relates to acyloxyalkyl carbamate prodrugs of3-aminopropylphosphinic acid and analogs thereof suitable for oraladministration and sustained release dosage forms.

BACKGROUND

(±)-4-Amino-3-(4-chlorophenyl)butanoic acid (baclofen), (1), is ananalog of gamma-aminobutyric acid (i.e., GABA) that selectivelyactivates GABA_(B) receptors, resulting in neuronal hyperpolarization.GABA_(B) receptors are located in laminae I-IV of the spinal cord, whereprimary sensory fibers end. These G-protein coupled receptors activateconductance by K⁺-selective ion channels and may reduce currentsmediated by Ca²⁺ channels in certain neurons. Baclofen has a presynapticinhibitory effect on the release of excitatory neurotransmitters andalso acts postsynaptically to decrease motor neuron firing (see Bowery,Trends Pharmacol. Sci. 1989, 10, 401-407; Misgeld et al., Prog.Neurobiol. 1995, 46, 423-462).

Many examples of compounds having antagonistic activity at GABA_(B)receptors exist and block the effects of baclofen in vitro and in vivo.Examples of GABA_(B) antagonists include certain aminophosphonic acids(e.g. phaclofen), aminosulfonic acids (e.g. saclofen and2-hydroxysaclofen), and aminophosphinic acids, particularly certain3-aminopropylphosphinic acids.

Certain 3-aminopropylphosphinic acid analog GABA_(B) antagonists aredescribed in Froestl et al., J. Med. Chem. 1995, 38, 3313-3331; Dingwallet al., Tetrahedron 1989, 45, 3787-3808; Deprele and Montchamp, J. Org.Chem. 2001, 66, 6745-6755; Dingwall et al., U.S. Pat. No. 4,656,298;Baylis et al., U.S. Pat. No. 5,013,863; Baylis et al., U.S. Pat. No.5,051,524; Baylis et al., U.S. Pat. No. 5,300,679; Marescaux et al.,U.S. Pat. No. 5,229,379; Marescaux et al., U.S. Pat. No. 5,407,922;Mickel et al., U.S. Pat. No. 5,332,729; Mickel, U.S. Pat. No. 5,376,684;and Mickel et al., U.S. Pat. No. 5,424,441. Examples ofaminopropylphosphinic analog GABA_(B) antagonists include:

-   3-Aminopropyl(n-butyl)phosphinic acid;-   3-Aminopropyl(diethoxymethyl)phosphinic acid;-   3-Aminopropyl(benzyl)phosphinic acid;-   3-Amino-2(S)-hydroxypropyl(benzyl)phosphinic acid;-   3-Amino-2-hydroxypropyl(cyclohexylmethyl)phosphinic acid;-   3-Amino-2(S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid;-   3-(4-Chlorobenzylamino)-2(R)-hydroxypropyl(benzyl)phosphinic acid;-   3-(4-Chlorobenzylamino)propyl(diethoxymethyl)phosphinic acid;-   3-(4-Chlorobenzylamino)-2-hydroxypropyl(n-butyl)phosphinic acid;-   3-(3,4-Dichlorobenzylamino)-2(S)-hydroxypropyl(benzyl)phosphinic    acid;-   3-(3,4-Dichlorobenzylamino)-2(S)-hydroxypropyl(diethoxymethyl)phosphinic    acid;-   3-(4-Chlorobenzylamino)propyl(cyclohexylmethyl)phosphinic acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1    (R)-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1(S)-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1    (R)-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1(S)-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1    (R)-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1(S)-(3,4-Dichlorophenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1(R)-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1(S)-(3,4-Dichlorophenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1    (R)-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1(S)-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1    (R)-(3-Carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1(S)-(3-carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(cyclohexylmethyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1-(3-Carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1    (R)-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1(S)-(3-Carboxyphenyl)ethyl]amino}-2(S)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1    (R)-(3-Carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;-   3-{N-[1(S)-(3-Carboxyphenyl)ethyl]amino}-2(R)-hydroxy-propyl-(benzyl)-phosphinic    acid;

pharmaceutically acceptable salts of any of the foregoing, andpharmaceutically acceptable solvates of any of the foregoing.

GABA_(B) antagonists are useful in the treatment of cognitive or memorydisorders including Mild Cognitive Impairment (MCI) and cognitiveimpairment associated with Alzheimer's disease (see e.g., Baylis et al.,U.S. Pat. No. 5,190,933; Pearlman et al., U.S. Application PublicationNo. 2002/0187977; Froestl et al., Biochem. Pharmacol. 2004, 68,1479-1487; Helm et al., Neuropharmacol. 2005, 48, 956-964; Mondadori etal., Behav. Brain Res. 1996, 77, 227-229; Mondadori et al., Behav.Neural Biol. 1993, 60, 62-68; and Nakagawa et al., Brain Res. 1997, 766,101-106).

GABA_(B) antagonists are also useful in the treatment of depressivemoods or anxiety states (see e.g., Slattery et al., J. Pharmacol. Exp.Ther. 2005, 312, 290-296; and Nakagawa et al., Eur. J. Pharmacol. 1999,381, 1-7).

GABA_(B) antagonists are also useful in the treatment of epilepsy,particularly “petit-mal” type epilepsy, including spontaneous absenceepilepsy and atypical absence epilepsy (see e.g., Marescaux et al., U.S.Pat. No. 5,407,922; Marescaux et al., U.S. Pat. No. 5,545,631; Czuczwarand Patsalos, CNS Drugs, 2001, 15, 339-350; Getova et al., Eur. J.Pharmacol. 1997, 320, 9-13; Vergnes et al., Eur. J. Pharmacol. 1997,332, 245-255; and Marescaux et al., J. Neural Transm. 1992, 35,179-188).

Typical ligands for GABA_(B) receptors such as baclofen and thezwitterionic 3-aminopropylphosphinic acids noted above are polarmolecules that lack the requisite physicochemical characteristics foreffective passive permeability across cellular membranes. For baclofen,passage of the drug across the gastrointestinal (GI) tract and theblood-brain barrier (BBB) is mediated primarily by active transportprocesses rather than by passive diffusion. Accordingly, baclofen is asubstrate for active transport mechanisms shared by neutral α-aminoacids such as leucine and β-amino acids such as β-alanine and taurine(van Bree et al., Pharm. Res. 1988, 5, 369-371; Cercos-Fortea et al.,Biopharm. Drug. Disp. 1995, 16, 563-577; Deguchi et al., Pharm. Res.1995, 12, 1838-1844; Moll-Navarro et al., J. Pharm. Sci. 1996, 85,1248-1254). 3-Aminopropylphosphinic acids are also likely to exploitrelated active transport mechanisms to permeate the GI mucosa followingoral administration.

Another common feature shared by baclofen and 3-aminopropylphosphinicacid GABA_(B) receptor antagonists is their rapid clearance from thesystemic circulation, which leads to the necessity for frequent dosingin humans (e.g. three or four times daily) (see Bowery, supra;“Commercial and Pipeline Perspectives: Upper GI Disorders”, Data MonitorReport, September 2004, p. 147; Gleiter et al., J. Clin. Pharm. 1996,36, 428-438; and Froestl et al., Biochem. Pharmacol. 2004, 68,1479-1487). Sustained release oral dosage formulations are aconventional solution to the problem of rapid systemic drug clearance,as is well known in the art (see e.g., “Remington's PharmaceuticalSciences,” Philadelphia College of Pharmacy and Science, 19th Edition,1995). Osmotic delivery systems are also recognized methods forsustained drug delivery (see e.g., Verma et al., Drug Dev. Ind. Pharm.2000, 26, 695-708). Successful application of these technologies dependson the drug of interest having an effective level of absorption from thelarge intestine (also referred to herein as the colon), where the dosageform spends a majority of its time during its passage down thegastrointestinal tract. Baclofen, and likely other zwitterionic GABA_(B)receptor ligands, is poorly absorbed following administration into thecolon in animal models (Merino et al., Biopharm. Drug. Disp. 1989, 10,279-297), presumably because the transporter proteins mediating baclofenabsorption in the upper region of the small intestine are not expressedin the large intestine. Development of an oral controlled releaseformulation for zwitterionic GABA_(B) receptor antagonists shouldconsiderably improve the convenience, efficacy, and side effect profileof GABA_(B) antagonist therapy. However, the rapid passage ofconventional dosage forms through the proximal absorptive region of thesmall intestine has thus far prevented the successful application ofsustained release technologies to these drugs. A number of exploratorydelivery technologies that rely on either mucoadhesion or gastricretention have been suggested to achieve sustained delivery of baclofen(Sinnreich, U.S. Pat. No. 4,996,058; Khanna, U.S. Pat. No. 5,091,184;Fara et al., supra; Dudhara et al., International Publication No. WO03/011255) though to date none of these appear to be able to achievesustained blood levels of baclofen in human subjects. More recently,acyloxyalkyl carbamate prodrugs of baclofen and analogs thereof havebeen shown to provide enhanced bioavailability of baclofen followingoral administration as described in co-pending application Gallop etal., International Publication No. WO 2005/019163 entitled “AcyloxyalkylCarbamate Prodrugs, Methods, Synthesis and Use,” filed Aug. 20, 2004.Thus, there is a need for new prodrugs of 3-aminopropylphosphinic acidGABA_(B) receptor antagonists, which are well absorbed in the largeintestine/colon and hence are suitable for oral sustained releaseformulations, thus improving the convenience, efficacy, and side effectprofile of GABA_(B) antagonist therapy.

SUMMARY

These and other needs are satisfied by the disclosure herein ofacyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acid andanalogs thereof, pharmaceutical compositions of acyloxyalkyl carbamateprodrugs of 3-aminopropylphosphinic acid and analogs thereof, methods ofmaking acyloxyalkyl carbamate prodrugs of 3-aminopropylphosphinic acidand analogs thereof, and methods of using acyloxyalkyl carbamateprodrugs of 3-aminopropylphosphinic acid and analogs thereof and/orpharmaceutical compositions thereof to treat various medical disorders.

In a first aspect, a compound of Formula (I) is provided:

pharmaceutically acceptable salts thereof, and pharmaceuticallyacceptable solvates of any of the foregoing, wherein:

R¹ is chosen from acyl, substituted acyl, alkyl, substituted alkyl,aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl,substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl,heteroalkyl, substituted heteroalkyl, heteroaryl, substitutedheteroaryl, heteroarylalkyl, and substituted heteroarylalkyl;

R² and R³ is chosen from hydrogen, alkyl, substituted alkyl,alkoxycarbonyl, substituted alkoxycarbonyl, aryl, substituted aryl,arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl,heteroaryl, substituted heteroaryl, heteroarylalkyl, and substitutedheteroarylalkyl, or R² and R³ together with the carbon atom to whichthey are bonded form a cycloalkyl, substituted cycloalkyl,cycloheteroalkyl, or substituted cycloheteroalkyl ring;

R⁴ is chosen from C₂₋₆ alkyl, substituted C₂₋₆ alkyl, benzyl,substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇ cycloalkylmethyl, anddialkoxymethyl;

R⁵ is chosen from hydrogen, hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl,substituted C₁₋₄ alkyl, aryl, substituted aryl, C₃₋₆ cycloalkyl,substituted C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl, C₇₋₉phenylalkyl, and substituted C₇₋₉ phenylalkyl;

R⁶ and R⁷ is chosen from hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl,substituted aryl, C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl,C₇₋₉ phenylalkyl, and substituted C₇₋₉ phenylalkyl; and

R⁸ is chosen from hydrogen, C₁₋₆ alkyl, substituted C₁₋₆ alkyl, aryl,substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl.

In a second aspect, pharmaceutical compositions comprising atherapeutically effective amount of a compound of Formula (I), or apharmaceutically acceptable salt, hydrate, or solvate thereof, and apharmaceutically acceptable vehicle such as a diluent, carrier,excipient, or adjuvant are provided. The choice of diluent, carrier,excipient, or adjuvant will depend upon, among other factors, thedesired mode of administration.

In a third aspect, methods are provided for treating cognitive or memorydisorders such as mild cognitive impairment and cognitive impairmentassociated with Alzheimer's disease, mood disorders such as depressionand anxiety, and movement disorders such as epilepsy. The methodsgenerally involve administering to a patient in need of such treatment atherapeutically effective amount of a compound of Formula (I) and/or apharmaceutical composition comprising a compound of Formula (I).

In a fourth aspect, a method of maintaining a therapeutically effectiveconcentration of a 3-aminopropylphosphinic acid analog in the bloodplasma of a patient for a time period chosen from at least about 4hours, at least about 8 hours, and at least about 12 hours, comprisingorally administering a pharmaceutical composition comprising thecorresponding compound of Formula (I) to the patient is provided.

DETAILED DESCRIPTION Definitions

A dash (“-”) that is not between two letters or symbols is used toindicate a point of attachment for a moiety or substituent. For example,—CONH₂ is a moiety bonded through the carbon atom.

“1-Acyloxy-Alkyl Carbamate” refers to an N-1-acyloxy-alkoxycarbonylderivative of a 3-aminopropylphosphinic acid analog as encompassed bycompounds of Formula (I) disclosed herein.

“Alkyl,” by itself or as part of another substituent, refers to asaturated or unsaturated, branched or straight-chain monovalenthydrocarbon radical derived by the removal of one hydrogen atom from asingle carbon atom of a parent alkane, alkene or alkyne. Examples ofalkyl groups include, but are not limited to, methyl; ethyls such asethanyl, ethenyl, and ethynyl; propyls such as propan-1-yl, propan-2-yl,prop-1-en-1-yl, prop-1-en-2-yl, prop-2-en-1-yl (allyl), prop-1-yn-1-yl,prop-2-yn-1-yl, etc.; butyls such as butan-1-yl, butan-2-yl,2-methyl-propan-1-yl, 2-methyl-propan-2-yl, but-1-en-1-yl,but-1-en-2-yl, 2-methyl-prop-1-en-1-yl, but-2-en-1-yl, but-2-en-2-yl,buta-1,3-dien-1-yl, buta-1,3-dien-2-yl, but-1-yn-1-yl, but-1-yn-3-yl,but-3-yn-1-yl, etc.; and the like.

The term “alkyl” is specifically intended to include groups having anydegree or level of saturation, i.e., groups having exclusively singlecarbon-carbon bonds, groups having one or more double carbon-carbonbonds, groups having one or more triple carbon-carbon bonds, and groupshaving mixtures of single, double, and triple carbon-carbon bonds. Wherea specific level of saturation is intended, the expressions “alkanyl,”“alkenyl,” and “alkynyl” are used. In certain embodiments, alkyl groupscomprise from 1 to 20 carbon atoms, in certain embodiments, from 1 to 10carbon atoms, and in certain embodiments, from 1 to 6 carbon atoms.

“Alkanyl,” by itself or as part of another substituent, refers to asaturated, branched or straight-chain alkyl radical derived by theremoval of one hydrogen atom from a single carbon atom of a parentalkane. Examples of alkanyl groups include, but are not limited to,methanyl; ethanyl; propanyls such as propan-1-yl, propan-2-yl(isopropyl), etc.; butanyls such as butan-1-yl, butan-2-yl (sec-butyl),

“Alkenyl,” by itself or as part of another substituent, refers to anunsaturated, branched or straight-chain alkyl radical having at leastone carbon-carbon double bond derived by the removal of one hydrogenatom from a single carbon atom of a parent alkene. The group may be ineither the cis or trans conformation about each double bond. Examples ofalkenyl groups include, but are not limited to, ethenyl; propenyls suchas prop-1-en-1-yl, prop-1-en-2-yl, prop-2-en-1-yl (allyl),prop-2-en-2-yl, butenyls such as but-1-en-1-yl, but-1-en-2-yl,2-methyl-prop-1-en-1-yl, but-2-en-1-yl, but-2-en-1-yl, but-2-en-2-yl,buta-1,3-dien-1-yl, buta-1,3-dien-2-yl, etc.; and the like.

“Alkynyl,” by itself or as part of another substituent, refers to anunsaturated, branched or straight-chain alkyl radical having at leastone carbon-carbon triple bond derived by the removal of one hydrogenatom from a single carbon atom of a parent alkyne. Examples of alkynylgroups include, but are not limited to, ethynyl; propynyls such asprop-1-yn-1-yl, prop-2-yn-1-yl, etc.; butynyls such as but-1-yn-1-yl,but-1-yn-3-yl, but-3-yn-1-yl, etc.; and the like.

“Acyl” by itself or as part of another substituent refers to the radical—C(O)R³⁰, where R³⁰ is chosen from hydrogen, alkyl, cycloalkyl,cycloheteroalkyl, aryl, arylalkyl, heteroalkyl, heteroaryl, andheteroarylalkyl as defined herein. Examples of acyl groups include, butare not limited to, formyl, acetyl, cyclohexylcarbonyl,cyclohexylmethylcarbonyl, benzoyl, benzylcarbonyl, and the like.

“Alkoxy,” by itself or as part of another substituent, refers to theradical —OR³¹ where R³¹ represents an alkyl or cycloalkyl group asdefined herein. Examples of alkoxy groups include, but are not limitedto, methoxy, ethoxy, propoxy, butoxy, cyclohexyloxy, and the like.

“Alkoxycarbonyl,” by itself or as part of another substituent, refers tothe radical —C(O)OR³² where R³² represents an alkyl or cycloalkyl groupas defined herein. Examples of alkoxycarbonyl groups include, but arenot limited to, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl,butoxycarbonyl, cyclohexyloxycarbonyl, and the like.

“Alkylamino,” by itself or as part of another substituent, refers to theradical —NHR³¹ where R³¹ is chosen from alkyl and cycloalkyl, as definedherein.

“3-Aminopropylphosphinic acid analog” refers to a compound of Formula(II):

wherein R⁴ is chosen from C₂₋₆ alkyl, substituted C₂₋₆ alkyl, benzyl,substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇ cycloalkylmethyl, anddialkoxymethyl;

R⁵ is chosen from hydrogen, hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl,substituted C₁₋₄ alkyl, aryl, substituted aryl, C₃₋₆ cycloalkyl,substituted C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl, C₇₋₉phenylalkyl, and substituted C₇₋₉ phenylalkyl;

R⁶ and R⁷ is chosen from hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl,substituted aryl, C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl,C₇₋₉ phenylalkyl, and substituted C₇₋₉ phenylalkyl; and

R⁸ is chosen from hydrogen, C₁₋₆ alkyl, substituted C₁₋₆ alkyl, aryl,substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl.

In certain embodiments of compounds of Formula (II), each of the one ormore substituent groups is independently chosen from halogen, C₁₋₃alkyl, —OH, —NH₂, —SH, —COOH, C₁₋₃ alkoxy, C₁₋₃ acyl, C₁₋₃ thioalkyl,C₁₋₃ alkoxycarbonyl, C₁₋₃ alkylamino, and C₁₋₃ dialkylamino.

Within the scope of this disclosure, it is to be understood that when R⁵is an oxo group the bond between R⁵ and the carbon to which it is bondedis a double bond.

“Aryl,” by itself or as part of another substituent, refers to amonovalent aromatic hydrocarbon radical derived by the removal of onehydrogen atom from a single carbon atom of a parent aromatic ringsystem. Aryl encompasses 5- and 6-membered carbocyclic aromatic rings,for example, benzene; bicyclic ring systems wherein at least one ring iscarbocyclic and aromatic, for example, naphthalene, indane, andtetralin; and tricyclic ring systems wherein at least one ring iscarbocyclic and aromatic, for example, fluorene. Aryl encompassesmultiple ring systems having at least one carbocyclic aromatic ringfused to at least one carbocylic aromatic ring, cycloalkyl ring, orheterocycloalkyl ring. For example, aryl includes 5- and 6-memberedcarbocyclic aromatic rings fused to a 5- to 7-membered heterocycloalkylring containing one or more heteroatoms chosen from N, O, and S. Forsuch fused, bicyclic ring systems wherein only one of the rings is acarbocyclic aromatic ring, the point of attachment may be at thecarbocyclic aromatic ring or the heterocycloalkyl ring. Examples of arylgroups include, but are not limited to, groups derived fromaceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene,benzene, chrysene, coronene, fluoranthene, fluorene, hexacene,hexaphene, hexylene, as-indacene, s-indacene, indane, indene,naphthalene, octacene, octaphene, octalene, ovalene, penta-2,4-diene,pentacene, pentalene, pentaphene, perylene, phenalene, phenanthrene,picene, pleiadene, pyrene, pyranthrene, rubicene, triphenylene,trinaphthalene, and the like. In certain embodiments, aryl groups havefrom 5 to 20 carbon atoms, and in certain embodiments, from 5 to 12carbon atoms. In certain embodiments, aryl has from 6 to 10 carbonatoms.

“Arylalkyl,” by itself or as part of another substituent, refers to anacyclic alkyl radical in which one of the hydrogen atoms bonded to acarbon atom, typically a terminal or sp³ carbon atom, is replaced withan aryl group. Examples of arylalkyl groups include, but are not limitedto, benzyl, 2-phenylethan-1-yl, 2-phenylethen-1-yl, naphthylmethyl,2-naphthylethan-1-yl, 2-naphthylethen-1-yl, naphthobenzyl,2-naphthophenylethan-1-yl, and the like. Where specific alkyl moietiesare intended, the nomenclature arylalkanyl, arylalkenyl, and/orarylalkynyl is used. In certain embodiments, an arylalkyl group is(C₇-C₃₀) arylalkyl, e.g., the alkanyl, alkenyl or alkynyl moiety of thearylalkyl group is (C₁-C₁₀) and the aryl moiety is (C₆-C₂₀), and incertain embodiments, an arylalkyl group is (C₇-C₂₀) arylalkyl, e.g., thealkanyl, alkenyl, or alkynyl moiety of the arylalkyl group is (C₁-C₈)and the aryl moiety is (C₆-C₂).

“AUC” is the area under a curve representing the concentration of acompound or metabolite thereof in a biological fluid in a patient as afunction of time following administration of the compound to thepatient. In certain embodiments, the compound is a prodrug and themetabolite is a drug. Examples of biological fluids include plasma andblood. The AUC may be determined by measuring the concentration of acompound or metabolite thereof in a biological fluid such as the plasmaor blood using methods such as liquid chromatography-tandem massspectrometry (LC/MS/MS), at various time intervals, and calculating thearea under the plasma concentration-versus-time curve. Suitable methodsfor calculating the AUC from a drug concentration-versus-time curve arewell known in the art. For example, an AUC for an α-amino acid may bedetermined by measuring the concentration of the α-amino acid in theplasma or blood of a patient following administration of a compound ofFormula (I) to the patient.

“C_(max)” is the maximum concentration of a drug in the plasma or bloodof a patient following administration of a dose of the drug or prodrugto the patient.

“Compounds” of Formula (I) disclosed herein include any specificcompounds within the formula whose structure is disclosed herein.Compounds may be identified by their chemical structure and/or chemicalname. If the chemical structure and chemical name conflict, the chemicalstructure is determinative of the identity of the compound.

The compounds described herein may comprise one or more chiral centersand/or double bonds and therefore may exist as stereoisomers such asdouble-bond isomers (i.e., geometric isomers), enantiomers, anddiastereomers. Accordingly, any chemical structures within the scope ofthe specification depicted, in whole or in part, with a relativeconfiguration encompass all possible enantiomers and stereoisomers ofthe illustrated compounds including the stereoisomerically pure form(e.g., geometrically pure, enantiomerically pure, or diastereomericallypure) and enantiomeric and stereoisomeric mixtures. Enantiomeric andstereoisomeric mixtures may be resolved into their component enantiomersor stereoisomers using separation techniques and stereoisomerically pureforms may be synthesized using chiral synthesis techniques well known tothe skilled artisan.

Compounds of Formula (I) include, but are not limited to, opticalisomers of compounds of Formula (I), racemates thereof, and othermixtures thereof. In such embodiments, the single enantiomers ordiastereomers, i.e., optically active forms may be obtained byasymmetric synthesis or by resolution of the racemates. Resolution ofthe racemates may be accomplished, for example, by conventional methodssuch as crystallization in the presence of a resolving agent, orchromatography, using, for example a chiral high-pressure liquidchromatography (HPLC) column. In addition, compounds of Formula (I)include Z- and E-forms (or cis- and trans-forms) of compounds withdouble bonds. In embodiments in which compounds of Formula (I) exist invarious tautomeric forms, compounds of Formula (I) include any and alltautomeric forms of the compound.

The compounds of Formula (I) may also exist in several tautomeric formsincluding the enol form, the keto form, and mixtures thereof.Accordingly, the chemical structures depicted herein encompass any andall possible tautomeric forms of the illustrated compounds. Thecompounds of Formula (I) also include isotopically labeled compoundswhere one or more atoms have an atomic mass different from the atomicmass conventionally found in nature. Examples of isotopes that may beincorporated into the compounds disclosed herein include, but are notlimited to, ²H, ³H, ¹¹C, ¹³C, ¹⁴C, ¹⁵N, ¹⁸O, ¹⁷O, etc. Compounds mayexist in unsolvated forms as well as solvated forms, including hydratedforms and as N-oxides. In general, compounds may be hydrates, solvates,or N-oxides. Certain compounds may exist in multiple crystalline oramorphous forms. Compounds of Formula (I) include pharmaceuticallyacceptable salts thereof, pharmaceutically acceptable solvates of thefree acid form of any of the foregoing, as well as crystalline forms ofany of the foregoing.

In general, all physical forms are equivalent for the uses contemplatedherein and are intended to be within the scope of the presentdisclosure. Further, it should be understood, when partial structures ofthe compounds are illustrated, that an asterisk indicates the point ofattachment of the partial structure to the rest of the molecule.

“Corresponding 3-aminopropylphosphinic acid analog” refers to a compoundof Formula (II) having the same R⁴, R⁵, R⁶, R⁷, and R⁸ groups as theacyloxyalkyl carbamate prodrug of the 3-aminopropylphosphinic acidanalog of Formula (I). The “corresponding acyloxyalkyl carbamateprodrug” refers to the compound of Formula (I) having the same R⁴, R⁵,R⁶, R⁷, and R⁸ groups as the 3-aminopropylphosphinic acid analog ofFormula (II)

“Cycloalkoxycarbonyl,” by itself or as part of another substituent,refers to the radical —C(O)OR³⁶ where R³⁶ represents an cycloalkyl groupas defined herein. Examples of cycloalkoxycarbonyl groups include, butare not limited to, cyclobutyloxycarbonyl, cyclohexyloxycarbonyl, andthe like.

“Cycloalkyl,” by itself or as part of another substituent, refers to asaturated or partially unsaturated cyclic alkyl radical. Where aspecific level of saturation is intended, the nomenclature“cycloalkanyl” or “cycloalkenyl” is used. Examples of cycloalkyl groupsinclude, but are not limited to, groups derived from cyclopropane,cyclobutane, cyclopentane, cyclohexane, and the like. In certainembodiments, the cycloalkyl group is C₃₋₁₀ cycloalkyl, and in certainembodiments C₃₋₇ cycloalkyl.

“Cycloheteroalkyl,” by itself or as part of another substituent, refersto a saturated or partially unsaturated cyclic alkyl radical in whichone or more carbon atoms (and any associated hydrogen atoms) is replacedwith the same or different heteroatom. Examples heteroatoms to replacethe carbon atom(s) include, but are not limited to, N, P, O, S, Si, etc.Where a specific level of saturation is intended, the nomenclature“cycloheteroalkanyl” or “cycloheteroalkenyl” is used. Examples ofcycloheteroalkyl groups include, but are not limited to, groups derivedfrom epoxides, azirines, thiiranes, imidazolidine, morpholine,piperazine, piperidine, pyrazolidine, pyrrolidine, quinuclidine, and thelike.

“Dialkylamino” by itself or as part of another substituent refers to theradical —NR⁴³R⁴⁴ where R⁴³ and R⁴⁴ are independently chosen from alkyl,cycloalkyl, cycloheteroalkyl, arylalkyl, heteroalkyl, andheteroarylalkyl, or R⁴³ and R⁴⁴ together with the nitrogen to which theyare bonded form a cycloheteroalkyl ring.

“Halogen” refers to a fluoro, chloro, bromo, or iodo group.

“Heteroalkyl, heteroalkanyl, heteroalkenyl, and heteroalkynyl,” bythemselves or as part of another substituent, refer to alkyl, alkanyl,alkenyl, and alkynyl groups, respectively, in which one or more of thecarbon atoms (and any associated hydrogen atoms) is replaced with thesame or different heteroatomic groups. Typical heteroatomic groups whichmay be included in these groups include, but are not limited to, —O—,—S—, —O—O—, —S—S—, —O—S—, —NR³⁷R³⁸—, ═N—N═, —N═N—, —N═N—NR³⁹R⁴⁰, —PR⁴¹—,—P(O)₂—, —POR⁴²—, —O—P(O)₂—, —SO—, —SO₂—, —SnR⁴³R⁴⁴— and the like, whereR³⁷, R³⁸, R³⁹, R⁴⁰, R⁴¹R⁴², and R⁴⁴ is hydrogen, alkyl, substitutedalkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl,cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substitutedcycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl,substituted heteroaryl, heteroarylalkyl, or substituted heteroarylalkyl.

“Heteroaryl,” by itself or as part of another substituent, refers to amonovalent heteroaromatic radical derived by the removal of one hydrogenatom from a single atom of a parent heteroaromatic ring system.Heteroaryl encompasses multiple ring systems having at least oneheteroaromatic ring fused to at least one other ring, which may bearomatic or non-aromatic. Heteroaryl encompasses 5- to 7-memberedaromatic, monocyclic rings containing one or more, for example, from 1to 4, or in certain embodiments, from 1 to 3, heteroatoms chosen from N,O, and S, with the remaining ring atoms being carbon; and bicyclicheterocycloalkyl rings containing one or more, for example, from 1 to 4,or in certain embodiments, from 1 to 3, heteroatoms chosen from N, O,and S, with the remaining ring atoms being carbon and wherein at leastone heteroatom is present in an aromatic ring. For example, heteroarylincludes a 5- to 7-membered heteroaromatic ring fused to a 5- to7-membered cycloalkyl ring. For such fused, bicyclic heteroaryl ringsystems wherein only one of the rings contains one or more heteroatoms,the point of attachment may be at the heteroaromatic ring or thecycloalkyl ring. In certain embodiments, when the total number of N, S,and O atoms in the heteroaryl group exceeds one, the heteroatoms are notadjacent to one another. In certain embodiments, the total number of N,S, and O atoms in the heteroaryl group is not more than two. In certainembodiments, the total number of N, S, and O atoms in the aromaticheterocycle is not more than one. Heteroaryl does not encompass oroverlap with aryl as defined herein.

Examples of heteroaryl groups include, but are not limited to, groupsderived from acridine, arsindole, carbazole, β-carboline, chromane,chromene, cinnoline, furan, imidazole, indazole, indole, indoline,indolizine, isobenzofuran, isochromene, isoindole, isoindoline,isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole,oxazole, perimidine, phenanthridine, phenanthroline, phenazine,phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine,pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline, quinoline,quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene,triazole, xanthene, and the like. In certain embodiments, a heteroarylgroup is a 5- to 20-membered heteroaryl, and in certain embodiments a 5-to 10-membered heteroaryl. In certain embodiments, heteroaryl groups arethose derived from thiophene, pyrrole, benzothiophene, benzofuran,indole, pyridine, quinoline, imidazole, oxazole, and pyrazine.

“Heteroarylalkyl,” by itself or as part of another substituent, refersto an acyclic alkyl radical in which one of the hydrogen atoms bonded toa carbon atom, typically a terminal or Sp³ carbon atom, is replaced witha heteroaryl group. Where specific alkyl moieties are intended, thenomenclature heteroarylalkanyl, heteroarylalkenyl, and heterorylalkynylis used. In certain embodiments, the heteroarylalkyl group is a 6-30membered heteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynyl moietyof the heteroarylalkyl is 1-10 membered and the heteroaryl moiety is a5-20-membered heteroaryl, and in certain embodiments, 6-20 memberedheteroarylalkyl, e.g., the alkanyl, alkenyl, or alkynyl moiety of theheteroarylalkyl is 1-8 membered and the heteroaryl moiety is a5-12-membered heteroaryl.

“Parent Aromatic Ring System” refers to an unsaturated cyclic orpolycyclic ring system having a conjugated π (pi) electron system.Specifically included within the definition of “parent aromatic ringsystem” are fused ring systems in which one or more of the rings arearomatic and one or more of the rings are saturated or unsaturated, forexample, fluorene, indane, indene, phenalene, etc. Typical parentaromatic ring systems include, but are not limited to, aceanthrylene,acenaphthylene, acephenanthrylene, anthracene, azulene, benzene,chrysene, coronene, fluoranthene, fluorene, hexacene, hexaphene,hexylene, as-indacene, s-indacene, indane, indene, naphthalene,octacene, octaphene, octalene, ovalene, penta-2,4-diene, pentacene,pentalene, pentaphene, perylene, phenalene, phenanthrene, picene,pleiadene, pyrene, pyranthrene, rubicene, triphenylene, trinaphthalene,and the like.

“Parent Heteroaromatic Ring System” refers to a parent aromatic ringsystem in which one or more carbon atoms (and any associated hydrogenatoms) is replaced with the same or different heteroatom. Typicalheteroatoms to replace the carbon atoms include, but are not limited to,N, P, O, S, Si, etc. Specifically included within the definition of“parent heteroaromatic ring systems” are fused ring systems in which oneor more of the rings are aromatic and one or more of the rings aresaturated or unsaturated, such as, for example, arsindole, benzodioxan,benzofuran, chromane, chromene, indole, indoline, xanthene, etc. Typicalparent heteroaromatic ring systems include, but are not limited to,arsindole, carbazole, β-carboline, chromane, chromene, cinnoline, furan,imidazole, indazole, indole, indoline, indolizine, isobenzofuran,isochromene, isoindole, isoindoline, isoquinoline, isothiazole,isoxazole, naphthyridine, oxadiazole, oxazole, perimidine,phenanthridine, phenanthroline, phenazine, phthalazine, pteridine,purine, pyran, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine,pyrrole, pyrrolizine, quinazoline, quinoline, quinolizine, quinoxaline,tetrazole, thiadiazole, thiazole, thiophene, triazole, xanthene, and thelike.

“Patient” includes mammals, such as for example, humans.

“Pharmaceutical composition” refers to at least one compound of Formula(I) and at least one pharmaceutically acceptable vehicle with which thecompound is to be administered to a patient.

“Pharmaceutically acceptable salt” refers to a salt of a compound, whichpossesses the desired pharmacological activity of the parent compound.Such salts include: (1) acid addition salts, formed with inorganic acidssuch as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid, and the like; or formed with organic acids such asacetic acid, propionic acid, hexanoic acid, cyclopentanepropionic acid,glycolic acid, pyruvic acid, lactic acid, malonic acid, succinic acid,malic acid, maleic acid, fumaric acid, tartaric acid, citric acid,benzoic acid, 3-(4-hydroxybenzoyl)benzoic acid, cinnamic acid, mandelicacid, methanesulfonic acid, ethanesulfonic acid, 1,2-ethane-disulfonicacid, 2-hydroxyethanesulfonic acid, benzenesulfonic acid,4-chlorobenzenesulfonic acid, 2-naphthalenesulfonic acid,4-toluenesulfonic acid, camphorsulfonic acid,4-methylbicyclo[2.2.2]-oct-2-ene-1-carboxylic acid, glucoheptonic acid,3-phenylpropionic acid, trimethylacetic acid, tertiary butylacetic acid,lauryl sulfuric acid, gluconic acid, glutamic acid, hydroxynaphthoicacid, salicylic acid, stearic acid, muconic acid, and the like; and (2)salts formed when an acidic proton present in the parent compound isreplaced by a metal ion, e.g., an alkali metal ion, an alkaline earthmetal ion, or an aluminum ion; or coordinates with an organic base suchas ethanolamine, diethanolamine, triethanolamine, N-methylglucamine, andthe like.

“Pharmaceutically acceptable vehicle” refers to a pharmaceuticallyacceptable diluent, a pharmaceutically acceptable adjuvant, apharmaceutically acceptable excipient, a pharmaceutically acceptablecarrier, or a combination of any of the foregoing with which thecompound of Formula (I) may be administered to a patient and which doesnot destroy the pharmacological activity thereof, and which is nontoxicwhen administered in doses sufficient to provide a therapeuticallyeffective amount of the compound.

“Pharmaceutically acceptable” refers to approved or approvable by aregulatory agency of a federal or a state government, listed in the U.S.Pharmacopoeia, or listed other generally recognized pharmacopoeia foruse in mammals, including humans.

“Prodrug” refers to a derivative of an active compound (drug) thatundergoes a transformation under the conditions of use, such as withinthe body, to release an active drug. Prodrugs are frequently, but notnecessarily, pharmacologically inactive until converted into the activedrug. Prodrugs may be obtained by bonding a promoiety (defined herein),typically via a functional group, to a drug.

“Promoiety” refers to a group bonded to a drug, typically to afunctional group of the drug, via bond(s) that are cleavable underspecified conditions of use. The bond(s) between the drug and promoietymay be cleaved by enzymatic or non-enzymatic means. Under the conditionsof use, for example following administration to a patient, the bond(s)between the drug and promoiety may be cleaved to release the parentdrug. The cleavage of the promoiety may proceed spontaneously, such asvia a hydrolysis reaction, or it may be catalyzed or induced by anotheragent, such as by an enzyme, by light, by acid, or by a change of orexposure to a physical or environmental parameter, such as a change oftemperature, pH, etc. The agent may be endogenous to the conditions ofuse, such as an enzyme present in the systemic circulation to which theprodrug is administered or the acidic conditions of the stomach, or theagent may be supplied exogenously. In certain embodiments, the drug is3-aminopropylphosphinic acid or analog thereof of Formula (II) and thepromoiety is an acyloxyalkyloxycarbonyl group having the structure:

where R¹, R², and R³ are defined herein.

“Protecting group” refers to a group of atoms, which when attached to areactive functional group in a molecule, masks, reduces, or preventsreactivity of the functional group. Examples of protecting groups can befound in Green et al., “Protective Groups in Organic Chemistry,” (Wiley,2^(nd) ed. 1991) and Harrison et al., “Compendium of Synthetic OrganicMethods,” Vols. 1-8 (John Wiley and Sons, 1971-1996). Representativeamino protecting groups include, but are not limited to, formyl, acetyl,trifluoroacetyl, benzyl, benzyloxycarbonyl (CBZ), tert-butoxycarbonyl(Boc), trimethylsilyl (TMS), 2-trimethylsilyl-ethanesulfonyl (SES),trityl and substituted trityl groups, allyloxycarbonyl,9-fluorenylmethyloxycarbonyl (FMOC), nitro-veratryloxycarbonyl (NVOC),and the like. Representative hydroxy protecting groups include, but arenot limited to, those where the hydroxy group is either acylated oralkylated such as benzyl, and trityl ethers as well as alkyl ethers,tetrahydropyranyl ethers, trialkylsilyl ethers, and allyl ethers.

“Pharmaceutically acceptable solvate” refers to a molecular complex of acompound with one or more solvent molecules in a stoichiometric ornon-stoichiometric amount. Such solvent molecules are those commonlyused in the pharmaceutical arts, e.g., water, ethanol, and the like. Amolecular complex of a compound or moiety of a compound and a solventcan be stabilized by non-covalent intra-molecular forces such as,electrostatic forces, van der Waals forces, and hydrogen bonds. The term“hydrate” refers to a complex in which the one or more solvent moleculesare water including monohydrates and hemi-hydrates.

“Substantially one diastereomer” refers to a compound containing 2 ormore stereogenic centers such that the diastereomeric excess (d.e.) ofthe compound is greater than or equal to 90%. In some embodiments, thed.e. is, for example, greater than or equal to 91%, 92%, 93%, 94%, 95%,96%, 97%, 98%, and 99%.

“Substituted” refers to a group in which one or more hydrogen atoms areindependently replaced with the same or different substituent(s).Examples of substituents include, but are not limited to, —X, —R⁶⁰, —O⁻,═O, —OR⁶⁰, —SR⁶⁰, —S⁻, ═S, —NR⁶⁰R⁶¹, ═NR⁶⁰, —CX₃, —CN, —CF₃, —OCN, —SCN,—NO, —NO₂, ═N₂, —N₃, —S(O)₂O⁻, —S(O)₂OH, —S(O)₂R⁶⁰, —OS(O₂)O⁻,—OS(O)₂R⁶⁰, —P(O)(O⁻)₂, —P(O)(OR⁶⁰)(O⁻), —OP(O)(OR⁶⁰)(OR⁶¹), —C(O)R⁶⁰,—C(S)R⁶⁰, —C(O)OR⁶⁰, —C(O)NR⁶⁰R⁶¹, —C(O)O⁻, —(S)OR⁶⁰, —NR⁶²C(O)NR⁶⁰R⁶¹,—NR⁶²C(S)NR⁶⁰R⁶¹, —NR⁶²C(NR⁶³)NR⁶⁰R⁶¹, —C(NR⁶²)NR⁶⁰OR⁶¹, —S(O)₂,NR⁶⁰R⁶¹, —NR⁶³S(O)₂R⁶⁰, —NR⁶³C(O)R¹⁰, and —S(O)R⁶⁰ where each X isindependently a halogen; each R⁶⁰ and R⁶¹ are independently chosen fromhydrogen, alkyl, substituted alkyl, alkoxy, substituted alkoxy,cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substitutedcycloheteroalkyl, aryl, substituted aryl, heteroaryl, substitutedheteroaryl, arylalkyl, substituted arylalkyl, heteroarylalkyl, andsubstituted heteroarylalkyl, or R⁶⁰ and R⁶¹, together with the nitrogenatom to which they are bonded, form a cycloheteroalkyl, substitutedcycloheteroalkyl, heteroaryl, or substituted heteroaryl ring; and eachR⁶² and R⁶³ are independently chosen from hydrogen, alkyl, substitutedalkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl,cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substitutedcycloheteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl,and substituted heteroarylalkyl, or R⁶² and R⁶³, together with the atomto which they are bonded, form one or more cycloheteroalkyl, substitutedcycloheteroalkyl, heteroaryl, or substituted heteroaryl rings. Incertain embodiments, a tertiary amine or aromatic nitrogen may besubstituted with one or more oxygen atoms to form the correspondingnitrogen oxide.

In certain embodiments of the compounds of Formula (I) and Formula (II),each of the one or more substituent groups is independently chosen fromhalogen, C₁₋₃ alkyl, —OH, —NH₂, —SH, —COOH, C₁₋₃ alkoxy, C₁₋₃ acyl, C₁₋₃thioalkyl, C₁₋₃ alkoxycarbonyl, C₁₋₃ alkylamino, and C₁₋₃ dialkylamino.

“Thioalkyl,” by itself or as part of another substituent, refers to theradical —SR⁴¹ where R⁴¹ is alkyl as defined herein. “Mercapto,” byitself or as part of another substituent, refers to the radical —SR⁴¹where R⁴¹ is hydrogen.

“Treating” or “treatment” of a disease refers to arresting orameliorating a disease, disorder, or at least one of the clinicalsymptoms of a disease or disorder. In certain embodiments, “treating” or“treatment” refers to arresting or ameliorating at least one physicalparameter of the disease or disorder, which may or may not bediscernible by the patient. In certain embodiments, “treating” or“treatment” refers to inhibiting or controlling the disease or disorder,either physically (e.g., stabilization of a discernible symptom),physiologically (e.g., stabilization of a physical parameter), or both.In certain embodiments, “treating” or “treatment” refers to delaying, insome cases indefinitely, the onset of a disease or disorder.

“Therapeutically effective amount” refers to the amount of a compoundthat, when administered to a subject for treating a disease, ordisorder, or at least one of the clinical symptoms of a disease ordisorder, is sufficient to affect such treatment of the disease,disorder, or symptom. The “therapeutically effective amount” may varydepending, for example, on the compound, the disease, disorder, and/orsymptoms of the disease, severity of the disease, disorder, and/orsymptoms of the disease, the age, weight, and/or health of the patientto be treated, and the judgment of the prescribing physician. Anappropriate amount in any given instance may be readily ascertained bythose skilled in the art or capable of determination by routineexperimentation.

Reference is now be made in detail to certain embodiments of compoundsand methods of the present disclosure. The disclosed embodiments are notintended to be limiting of the claims. To the contrary, the claims areintended to cover all alternatives, modifications, and equivalents.

Compounds

In a first aspect, compounds of Formula (I) are provided:

and pharmaceutically acceptable salts of any of the foregoing, andpharmaceutically acceptable solvates of any of the foregoing, wherein:

R¹ is chosen from acyl, substituted acyl, alkyl, substituted alkyl,aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl,substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl,heteroalkyl, substituted heteroalkyl, heteroaryl, substitutedheteroaryl, heteroarylalkyl, and substituted heteroarylalkyl;

R² and R³ is chosen from hydrogen, alkyl, substituted alkyl,alkoxycarbonyl, substituted alkoxycarbonyl, aryl, substituted aryl,arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl,heteroaryl, substituted heteroaryl, heteroarylalkyl, and substitutedheteroarylalkyl, or R² and R³ together with the carbon atom to whichthey are bonded form a cycloalkyl, substituted cycloalkyl,cycloheteroalkyl, or substituted cycloheteroalkyl ring;

R⁴ is chosen from C₂₋₆ alkyl, substituted C₂₋₆ alkyl, benzyl,substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇ cycloalkylmethyl, anddialkoxymethyl;

R⁵ is chosen from hydrogen, hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl,substituted C₁₋₄ alkyl, aryl, substituted aryl, C₃₋₆ cycloalkyl,substituted C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl, C₇₋₉phenylalkyl, and substituted C₇₋₉ phenylalkyl;

R⁶ and R⁷ is chosen from hydrogen, C₁₋₆ alkyl, C₁₋₆ alkoxy, aryl,substituted aryl, C₃₋₆ cycloalkyl, heteroaryl, substituted heteroaryl,C₇₋₉ phenylalkyl, and substituted C₇₋₉ phenylalkyl; and

R⁸ is chosen from hydrogen, C₁₋₆ alkyl, substituted C₁₋₆ alkyl, aryl,substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl.

In certain embodiments of compounds of Formula (I), each of the one ormore substituent groups is independently chosen from halogen, C₁₋₃alkyl, —OH, —NH₂, —SH, —COOH, C₁₋₃ alkoxy, C₁₋₃ acyl, C₁₋₃ thioalkyl,C₁₋₃ alkoxycarbonyl, C₁₋₃ alkylamino, and C₁₋₃ dialkylamino.

Within the scope of this disclosure, it is to be understood that when R⁵is an oxo group the bond between R⁵ and the carbon to which it is bondedis a double bond.

In certain embodiments, each of R⁶, R⁷ and R⁸ is hydrogen.

In certain embodiments, R⁴ is chosen from ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl, 2-methylallyl,but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl, pent-3-ynyl, cyclohexyl,cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl,cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl, 3-methoxypropyl,3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl, 1-hydroxyisobutyl,benzyl, 1-hydroxybenzyl, and diethoxymethyl.

In certain embodiments, R⁴ is ethyl.

In certain embodiments, R⁴ is n-propyl.

In certain embodiments, R⁴ is n-butyl.

In certain embodiments, R⁴ is diethoxymethyl.

In certain embodiments, R⁴ is cyclohexylmethyl.

In certain embodiments, R⁴ is benzyl.

In certain embodiments, R⁵ is hydrogen, hydroxy, fluoro, oxo, or4-chlorophenyl. In other embodiments, R⁴ is ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl, 2-methylallyl,but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl, pent-3-ynyl, cyclohexyl,cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl,cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl, 3-methoxypropyl,3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl, 1-hydroxyisobutyl,benzyl, 1-hydroxybenzyl, or diethoxymethyl, R⁵ is hydrogen, hydroxy,fluoro, oxo, or 4-chlorophenyl, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R configuration. In other embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of compounds of Formula (I), R¹ is chosen fromC₁₋₆ alkyl, substituted C₁₋₆ alkyl, C₃₋₆ cycloalkyl, phenyl, substitutedphenyl, C₇₋₉ phenylalkyl, and pyridyl. In other embodiments of compoundsof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,neopentyl, 1,1-dimethoxyethyl, 1,1-diethoxyethyl, phenyl,4-methoxyphenyl, benzyl, phenethyl, styryl, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, 2-pyridyl, 3-pyridyl, or 4-pyridyl. In certainembodiments of compounds of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, cyclohexyl,or 3-pyridyl.

In certain embodiments of compounds of Formula (I), R¹ is chosen frompropyl, isopropyl, tert-butyl, cyclohexyl, and phenyl.

In certain embodiments of compounds of Formula (I), R² is chosen fromhydrogen, methyl, and isopropyl; and R³ is hydrogen.

In certain embodiments of compounds of Formula (I), R³ is hydrogen.

In certain embodiments of compounds of Formula (I), R⁴ is n-butyl.

In certain embodiments of compounds of Formula (I), R⁵ is chosen fromhydrogen and hydroxy.

In certain embodiments of compounds of Formula (I), R¹ is chosen frompropyl, isopropyl, tert-butyl, cyclohexyl, and phenyl; R² is chosen fromhydrogen, methyl, and isopropyl; R⁴ is n-butyl; and each of R³, R⁵, R⁶,R⁷, and R⁸ is hydrogen.

In certain embodiments of compounds of Formula (I), R² and R³ is chosenfrom hydrogen, alkyl, substituted alkyl, alkoxycarbonyl, substitutedalkoxycarbonyl, aryl, substituted aryl, arylalkyl, substitutedarylalkyl, carbamoyl, cycloalkyl, substituted cycloalkyl,cycloalkoxycarbonyl, substituted cycloalkoxycarbonyl, heteroaryl,substituted heteroaryl, heteroarylalkyl and substituted heteroarylalkyl.In certain embodiments of compounds of Formula (I), R² and R³ is chosenfrom hydrogen, C₁₋₄ alkyl, substituted C₁₋₄ alkyl, C₁₋₄ alkoxycarbonyl,C₃₋₆ cycloalkyl, C₃₋₆ cycloalkoxycarbonyl, phenyl, substituted phenyl,C₇₋₉ phenylalkyl, and pyridyl. In certain embodiments of compounds ofFormula (I), R² and R³ is chosen from hydrogen, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentyl,cyclohexyl, methoxycarbonyl, ethoxycarbonyl, isopropoxycarbonyl,cyclohexyloxycarbonyl, phenyl, benzyl, phenethyl, 2-pyridyl, 3-pyridyl,and 4-pyridyl. In certain embodiments of compounds of Formula (I), R² ishydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, methoxycarbonyl,ethoxycarbonyl, isopropoxycarbonyl, cyclohexyloxycarbonyl, phenyl,benzyl, phenethyl, 2-pyridyl, 3-pyridyl, or 4-pyridyl, and R³ ishydrogen. In certain embodiments of compounds of Formula (I), R² ishydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, phenyl, or cyclohexyl, and R³ is hydrogen. In certainembodiments of a compound of Formula (I), R² is methyl, methoxycarbonyl,ethoxycarbonyl, isopropoxycarbonyl, or cyclohexyloxycarbonyl, and R³ ismethyl.

In certain embodiments of a compound of Formula (I), R² and R³ togetherwith the carbon atom to which they are bonded form a cycloalkyl,substituted cycloalkyl, cycloheteroalkyl, or substitutedcycloheteroalkyl ring. In certain embodiments of compounds of Formula(I), R² and R³ together with the carbon atom to which they are bondedform a cyclobutyl, cyclopentyl, or cyclohexyl ring.

In certain embodiments of a compound of Formula (I), R¹ is chosen fromC₁₋₆ alkyl, substituted C₁₋₆ alkyl, C₃₋₆ cycloalkyl, phenyl, substitutedphenyl, C₇₋₉ phenylalkyl and pyridyl, and R² and R³ is chosen fromhydrogen, C₁₋₄ alkyl, substituted C₁₋₄ alkyl, C₁₋₄ alkoxycarbonyl, C₃₋₆cycloalkyl, C₃₋₆ cycloalkoxycarbonyl, phenyl, substituted phenyl, C₇₋₉phenylalkyl and pyridyl. In certain of the above embodiments, R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-dimethoxyethyl, 1,1-diethoxyethyl, phenyl, 4-methoxyphenyl, benzyl,phenethyl, styryl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,2-pyridyl, 3-pyridyl, or 4-pyridyl, and in certain embodiments, R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-diethoxyethyl, phenyl, cyclohexyl, or 3-pyridyl. In certain of theabove embodiments of a compound of Formula (I), R⁴ is ethyl, n-propyl,n-butyl, diethoxymethyl, cyclohexylmethyl, or benzyl, and R⁵ ishydrogen, hydroxy, fluoro, oxo, or 4-chlorophenyl.

In certain embodiments of a compound of Formula (I), R¹ is chosen fromC₁₋₆ alkyl, substituted C₁₋₆ alkyl, C₃₋₆ cycloalkyl, phenyl, substitutedphenyl, C₇₋₉ phenylalkyl, and pyridyl, R² and R³ is chosen fromhydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, methoxycarbonyl,ethoxycarbonyl, isopropoxycarbonyl, cyclohexyloxycarbonyl, phenyl,benzyl, phenethyl, 2-pyridyl, 3-pyridyl, and 4-pyridyl. In certain ofthe above embodiments, R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,sec-pentyl, neopentyl, 1,1-dimethoxyethyl, 1,1-diethoxyethyl, phenyl,4-methoxyphenyl, benzyl, phenethyl, styryl, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, 2-pyridyl, 3-pyridyl, or 4-pyridyl, and incertain embodiments, R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,neopentyl, 1,1-diethoxyethyl, phenyl, cyclohexyl, or 3-pyridyl. Incertain of the above embodiments of a compound of Formula (I), R⁴ isethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,n-pentyl, isopentyl, sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl,2-methylallyl, but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl,pent-3-ynyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl,cyclopentylmethyl, cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl,3-methoxypropyl, 3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl,1-hydroxyisobutyl, benzyl, 1-hydroxybenzyl, or diethoxymethyl, incertain embodiments, R⁴ is ethyl, n-propyl, n-butyl, diethoxymethyl,cyclohexylmethyl, or benzyl, R⁵ is hydrogen, hydroxy, fluoro, oxo, or4-chlorophenyl, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is chosen fromC₁₋₆ alkyl, substituted C₁₋₆ alkyl, C₃₋₆ cycloalkyl, phenyl, substitutedphenyl, C₇₋₉ phenylalkyl and pyridyl, R² is hydrogen, methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, phenyl, orcyclohexyl, and R³ is hydrogen. In certain of the above embodiments, R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-dimethoxyethyl, 1,1-diethoxyethyl, phenyl, 4-methoxyphenyl, benzyl,phenethyl, styryl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,2-pyridyl, 3-pyridyl, or 4-pyridyl, and in certain embodiments, R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-diethoxyethyl, phenyl, cyclohexyl, or 3-pyridyl. In certain of theabove embodiments of a compound of Formula (I), R⁴ is ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl,2-methylallyl, but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl,pent-3-ynyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl,cyclopentylmethyl, cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl,3-methoxypropyl, 3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl,1-hydroxyisobutyl, benzyl, 1-hydroxybenzyl, or diethoxymethyl, and incertain embodiments, R⁴ is ethyl, n-propyl, n-butyl, diethoxymethyl,cyclohexylmethyl, or benzyl, R⁵ is hydrogen, hydroxy, fluoro, oxo, or4-chlorophenyl, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, cyclohexyl,2-pyridyl, 3-pyridyl, or 4-pyridyl, R² is hydrogen, methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, phenyl, orcyclohexyl, R³ is hydrogen, R⁴ is ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,neopentyl, n-hexyl, n-heptyl, allyl, 2-methylallyl, but-3-enyl,propargyl, but-2-ynyl, but-3-ynyl, pent-3-ynyl, cyclohexyl,cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl,cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl, 3-methoxypropyl,3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl, 1-hydroxyisobutyl,benzyl, 1-hydroxybenzyl, or diethoxymethyl, R⁵ is hydrogen, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of compounds ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,neopentyl, 1,1-diethoxyethyl, phenyl, cyclohexyl, 2-pyridyl, 3-pyridyl,or 4-pyridyl, R² is hydrogen, methyl, n-propyl, or isopropyl, R³ ishydrogen, R⁴ is ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,n-hexyl, n-heptyl, allyl, 2-methylallyl, but-3-enyl, propargyl,but-2-ynyl, but-3-ynyl, pent-3-ynyl, cyclohexyl, cyclopropylmethyl,cyclobutylmethyl, cyclopentylmethyl, cyclohexylmethyl,cycloheptylmethyl, 2-methoxyethyl, 3-methoxypropyl, 3-ethoxypropyl,1-hydroxyethyl, 1-hydroxybutyl, 1-hydroxyisobutyl, benzyl,1-hydroxybenzyl, or diethoxymethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of compounds of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, methyl,n-propyl, or isopropyl, R³ is hydrogen, R⁴ is ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl,2-methylallyl, but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl,pent-3-ynyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl,cyclopentylmethyl, cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl,3-methoxypropyl, 3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl,1-hydroxyisobutyl, benzyl, 1-hydroxybenzyl, or diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof compounds of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, methyl, n-propyl, or isopropyl, R³ ishydrogen, R⁴ is ethyl, n-propyl, n-butyl, cyclohexylmethyl, benzyl, ordiethoxymethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.In certain embodiments of compounds of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, methyl, n-propyl, orisopropyl, R³ is hydrogen, R⁴ is ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,neopentyl, n-hexyl, n-heptyl, allyl, 2-methylallyl, but-3-enyl,propargyl, but-2-ynyl, but-3-ynyl, pent-3-ynyl, cyclohexyl,cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl,cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl, 3-methoxypropyl,3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl, 1-hydroxyisobutyl,benzyl, 1-hydroxybenzyl, or diethoxymethyl, R⁵ is hydrogen, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of compounds ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, methyl, n-propyl, or isopropyl, R³ is hydrogen, R⁴ is n-butyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of compounds of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, methyl, n-propyl, or isopropyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷ andR⁸ is hydrogen. In certain embodiments of compounds of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, methyl,n-propyl, or isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Inother embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷ and R⁸ is hydrogen. In other embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷ and R⁸ is hydrogen. In other embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopropylmethyl, R¹is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclobutylmethyl, R¹is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵¹ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷ and R⁸ is hydrogen. In other embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷ and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R¹ is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl; isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen, andeach of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is hydrogen, and each ofR⁶, R⁷, and R⁸ is hydrogen. In other embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is hydrogen, and each of R⁶,R⁷, and R⁸ is hydrogen. In other embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is propargyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R³ is ethyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is hydrogen, and each of R⁶, R⁷,and R⁸ is hydrogen. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ ishydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen. In other embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, and each of R⁶, R⁷, andR⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In otherembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In other embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is allyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-propyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is allyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is allyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-propyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is allyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is hydrogen, and each of R⁶, R⁷, and R⁸ is hydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R² is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is hydroxy, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is hydroxy, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is propargyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is hydroxy, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is hydroxy, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is propargyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the R configuration. In certain of the above embodimentsof a compound of Formula (I), the carbon to which R⁵ is bonded is of theS configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is hydroxy,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is allyl, R⁵ is hydroxy, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is hydroxy, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is hydroxy, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is propargyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is hydroxy, and each of R⁶; R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is hydroxy, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is allyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is propargyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ ishydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is hydroxy, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the R configuration. In certain of the above embodimentsof a compound of Formula (I), the carbon to which R⁵ is bonded is of theS configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is 1-hydroxy benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is fluoro, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is fluoro, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is propargyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is allyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is fluoro, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is fluoro, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl,R³ is hydrogen, R⁴ is propargyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁵ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is independently hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is independently hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ isindependently hydrogen. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of the Rconfiguration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the R configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of the Sconfiguration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisopropyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisobutyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ issec-butyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ istert-butyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-pentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isisopentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ issec-pentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isneopentyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-hexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isn-heptyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is allyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the R configuration. In certain of the above embodimentsof a compound of Formula (I), the carbon to which R⁵ is bonded is of theS configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is fluoro, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is fluoro, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is propargyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is fluoro, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, and each of R⁶, R⁷, and R⁸is hydrogen. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R configuration.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S configuration.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is allyl, R⁵ is fluoro,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is propargyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclobutylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclopentylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cycloheptylmethyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-methoxypropyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl,R⁵ is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ isfluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybenzyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵is fluoro, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the R configuration. In certain of the above embodimentsof a compound of Formula (I), the carbon to which R⁵ is bonded is of theS configuration.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is ethyl,R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 1 hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, and each of R⁶, R⁷, andR⁸ is hydrogen. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁵ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is allyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is propargyl, R¹ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is allyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo, andeach of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is isobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is sec-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is tert-butyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is isopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is sec-pentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is neopentyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-hexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-heptyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is allyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl; isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isopropyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isobutyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is sec-butyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is tert-butyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-pentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is isopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is sec-pentyl, R⁵ isoxo, and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is neopentyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-hexyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-heptyl, R⁵ is oxo,and each of R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is allyl, R⁵ is oxo, andeach of R⁶, R⁷; and R⁸ is hydrogen. In certain embodiments of a compoundof Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 2-methylallyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is but-3-enyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is propargyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is but-2-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is but-3-ynyl, R⁵ is oxo, and each of R⁶,R⁷, and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is pent-3-ynyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclohexyl, R⁵ is oxo, and each of R⁶,R⁷ and R⁸ is hydrogen. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclopropylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclobutylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclopentylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cycloheptylmethyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 2-methoxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 3-methoxypropyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 3-ethoxypropyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyethyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxybutyl, R⁵ is oxo, and each ofR⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is 1-hydroxyisobutyl, R⁵ is oxo, and eachof R⁶, R⁷, and R⁸ is hydrogen. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, and each of R⁶, R⁷,and R⁸ is hydrogen. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is 1-hydroxybenzyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸is hydrogen. In certain embodiments of a compound of Formula (I), R¹ ismethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, and each of R⁶, R⁷, and R⁸ ishydrogen.

In certain embodiments of a compound of Formula (I), R¹ is chosen fromC₁₋₆ alkyl, substituted C₁₋₆ alkyl, C₃₋₆ cycloalkyl, phenyl, substitutedphenyl, C₇₋₉ phenylalkyl and pyridyl, R² is chosen from hydrogen, C₁₋₄alkyl, substituted C₁₋₄ alkyl, C₁₋₄ alkoxycarbonyl, C₃₋₆ cycloalkyl,C₃₋₆ cycloalkoxycarbonyl, phenyl, substituted phenyl, C₇₋₉ phenylalkyland pyridyl, R³ is hydrogen, R⁴ is chosen from C₂₋₆ alkyl, substitutedC₂₋₆ alkyl, benzyl, substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇cycloalkylmethyl and dialkoxymethyl, R⁵ is chosen from hydrogen,hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl, aryl, substituted aryl, C₃₋₆cycloalkyl, heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl andsubstituted C₇₋₉ phenylalkyl, each of R⁶ and R⁷ is hydrogen, and R⁸ isC₇₋₉ phenylalkyl, or substituted C₇₋₉ phenylalkyl. In certain of theabove embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, 1,1-dimethoxyethyl, 1,1-diethoxyethyl,phenyl, 4-methoxyphenyl, benzyl, phenethyl, styryl, cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, 2-pyridyl, 3-pyridyl, or 4-pyridyl,and in certain embodiments, R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,sec-pentyl, neopentyl, 1,1-diethoxyethyl, phenyl, cyclohexyl, or3-pyridyl. In certain of the above embodiments of a compound of Formula(I), R² is hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl,benzyl, phenethyl, 2-pyridyl, 3-pyridyl, or 4-pyridyl, and in certainembodiments, R² is hydrogen, methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, cyclohexyl, or phenyl. Incertain of the above embodiments of a compound of Formula (I), R⁴ isethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,n-pentyl, isopentyl, sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl,2-methylallyl, but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl,pent-3-ynyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl,cyclopentylmethyl, cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl,3-methoxypropyl, 3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl,1-hydroxyisobutyl, benzyl, 1-hydroxybenzyl, or diethoxymethyl, and incertain embodiments, R⁴ is ethyl, n-propyl, n-butyl, diethoxymethyl,cyclohexylmethyl, or benzyl. In certain of the above embodiments of acompound of Formula (I), R⁵ is hydrogen, hydroxy, fluoro, oxo, or4-chlorophenyl. In certain of the above embodiments of a compound ofFormula (I), R⁸ is 3,5-dichlorobenzyl, 1-(3-chlorophenyl)ethyl,1-(3,4-dichlorophenyl)ethyl, 1-(3-chloro-4-iodophenyl)ethyl,1-(4-chloro-3-iodophenyl)ethyl, 3,4-dimethylbenzyl,1-(2,4-dimethoxyphenyl)ethyl, 1-(2,5-dimethoxyphenyl)ethyl,1-(2,6-dimethoxyphenyl)ethyl, 1-(3,4-dimethoxyphenyl)ethyl,1-(3,5-dimethoxyphenyl)ethyl, 1-(3,4,5-trimethoxyphenyl)ethyl,3-carboxybenzyl, 3-cyanobenzyl, 4-carboxybenzyl, 4-cyanobenzyl,1-(3-carboxyphenyl)ethyl, 1-(3-cyanophenyl)ethyl,1-(4-carboxyphenyl)ethyl, 1-(4-cyanophenyl)ethyl, 3-phenylprop-2-yl,2-(3,4-dichlorophenyl)propyl, 3-(3,4-dichlorophenyl)prop-2-yl, or3-phenyl-3-hydroxyprop-2-yl, and in certain embodiments R⁸ is1-(3,4-dichlorophenyl)ethyl, 1-(3-carboxyphenyl)ethyl,1-(4-carboxyphenyl)ethyl, 3,5-dichlorobenzyl, 3-carboxybenzyl, or4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In stillcertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the S-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration. In certainof the above embodiments of a compound of Formula (I), the carbon towhich R⁵ is bonded is of the R-configuration and the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3,4-dichlorophenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3,4-dichlorophenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3,4-dichlorophenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3,4-dichlorophenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3,4-dichlorophenyl)ethyl group is of the S-configuration. In certainof the above embodiments of a compound of Formula (I), the α-carbon ofthe 1-(3,4-dichlorophenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R¹ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(3-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(3-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(3-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(3-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(3-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R³ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydrogen, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is fluoro, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the S-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration. Incertain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the R-configuration and the α-carbonof the 1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is fluoro, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl,R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of theabove embodiments of a compound of Formula (I), the carbon to which R⁵is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the S-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration and the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain of the aboveembodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the α-carbon of the1-(4-carboxyphenyl)ethyl group is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is1-(4-carboxyphenyl)ethyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 1-(4-carboxyphenyl)ethyl. Incertain of the above embodiments of a compound of Formula (I), theα-carbon of the 1-(4-carboxyphenyl)ethyl group is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the α-carbon of the 1-(4-carboxyphenyl)ethyl group is ofthe R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is ethyl, R⁵is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is cyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is cyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain of the aboveembodiments of a compound of Formula (I), the carbon to which R⁵ isbonded is of the S-configuration. In certain of the above embodiments ofa compound of Formula (I), the carbon to which R⁵ is bonded is of theR-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R³ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo,each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certainembodiments of a compound of Formula (I), R¹ is methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl,or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is ethyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is n-propyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isn-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I): R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3,5-dichlorobenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3,5-dichlorobenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3,5-dichlorobenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3,5-dichlorobenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3,5-dichlorobenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl; n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁵is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁵ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR² is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl; isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is ethyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-propyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is n-butyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isdiethoxymethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is cyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ ishydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl, R⁵ is oxo, eachof R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 3-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 3-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 3-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 3-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is3-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 3-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In other embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In other embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁶ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁵ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydrogen, each of R⁶and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydrogen, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I) R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is ethyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isn-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is hydroxy, each ofR⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodimentsof a compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.In certain of the above embodiments of a compound of Formula (I), thecarbon to which R⁵ is bonded is of the S-configuration. In certain ofthe above embodiments of a compound of Formula (I), the carbon to whichR⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁵ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁵is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is hydroxy, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ ishydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl. In certain embodiments of a compound of Formula (I),R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is hydroxy, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain of the above embodiments of acompound of Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷ ishydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is fluoro, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isfluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is fluoro, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain of the above embodiments of a compoundof Formula (I), the carbon to which R⁵ is bonded is of theS-configuration. In certain of the above embodiments of a compound ofFormula (I), the carbon to which R⁵ is bonded is of the R-configuration.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is hydrogen,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ishydrogen, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is hydrogen, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is methyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² ismethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is methyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is ethyl, R³is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isethyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is ethyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-propyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-propyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-propyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisopropyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isopropyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is n-butyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isn-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is n-butyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is isobutyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isisobutyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments ofa compound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is isobutyl, R³ is hydrogen, R⁴ is benzyl,R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² issec-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is sec-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² istert-butyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is tert-butyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ isethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is phenyl,R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen,and R⁸ is 4-carboxybenzyl. In certain embodiments of a compound ofFormula (I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² isphenyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ is oxo, each of R⁶ andR⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is cyclohexylmethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is phenyl, R³ is hydrogen, R⁴ is benzyl, R⁵is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), R¹ is methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴is ethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is n-propyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, andR⁸ is 4-carboxybenzyl. In certain embodiments of a compound of Formula(I), R¹ is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² iscyclohexyl, R³ is hydrogen, R⁴ is n-butyl, R⁵ is oxo, each of R⁶ and R⁷is hydrogen, and R⁸ is 4-carboxybenzyl. In certain embodiments of acompound of Formula (I), R¹ is methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, cyclohexyl, or3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ is diethoxymethyl, R⁵ isoxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is 4-carboxybenzyl. Incertain embodiments of a compound of Formula (I), R¹ is methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl,cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ is hydrogen, R⁴ iscyclohexylmethyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸ is4-carboxybenzyl. In certain embodiments of a compound of Formula (I), R¹is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, phenyl, cyclohexyl, or 3-pyridyl, R² is cyclohexyl, R³ ishydrogen, R⁴ is benzyl, R⁵ is oxo, each of R⁶ and R⁷ is hydrogen, and R⁸is 4-carboxybenzyl.

In certain embodiments of a compound of Formula (I), the compound ischosen from:

-   3-{[1-isobutanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic    acid;-   3-{[benzoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid;-   3-{[1-isobutanoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic    acid;-   3-{[benzoyloxymethoxycarbonylamino}propyl(n-butyl)phosphinic acid;-   3-{[1-isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinic    acid;-   (3-{[1-cyclohexanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic    acid;-   3-{[1-isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinic    acid sodium salt;-   3-{[butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid    sodium salt;

a pharmaceutically acceptable salt of any of the foregoing, and apharmaceutically acceptable solvate of any of the foregoing.

Synthesis

The compounds disclosed herein may be obtained via the synthetic methodillustrated in Scheme 1. Those of ordinary skill in the art willappreciate that a synthetic route to the disclosed compounds consists ofattaching promoieties to 3-aminopropylphosphinic acid analogs. Numerousmethods have been described in the art for the synthesis of3-aminopropylphosphinic acid analog GABA_(B) antagonists (e.g. Froestlet al., J. Med. Chem. 1995, 38, 3313-3331; Dingwall et al., Tetrahedron1989, 45, 3787-3808; Deprele and Montchamp, J. Org. Chem. 2001, 66,6745-6755; Dingwall et al., U.S. Pat. No. 4,656,298; Baylis et al., U.S.Pat. No. 5,013,863; Baylis et al., U.S. Pat. No. 5,051,524; Baylis etal., U.S. Pat. No. 5,300,679; Marescaux et al., U.S. Pat. No. 5,229,379;Marescaux et al., U.S. Pat. No. 5,407,922; Mickel et al., U.S. Pat. No.5,332,729; Mickel, U.S. Pat. No. 5,376,684; and Mickel et al., U.S. Pat.No. 5,424,441). General synthetic methods useful in the synthesis of thecompounds described herein are available in the art (see, e.g., Wuts andGreene, “Protective Groups in Organic Synthesis,” John Wiley & Sons, 4thed. 2007; Harrison et al., “Compendium of Organic Synthetic Methods,”Vols. 1-11, John Wiley & Sons 1971-2003; Larock “Comprehensive OrganicTransformations,” John Wiley & Sons, 2nd ed. 2000; and Paquette,“Encyclopedia of Reagents for Organic Synthesis,” John Wiley & Sons,11th ed. 2003). Accordingly, starting materials useful for preparingcompounds and intermediates thereof, and/or practicing methods describedherein are commercially available or may be prepared by well-knownsynthetic methods. Other methods for synthesis of the prodrugs describedherein are either described in the art or will be readily apparent tothe skilled artisan in view of the references provided above and may beused to synthesize the compounds described herein. Accordingly, themethods presented in the Schemes herein are illustrative rather thancomprehensive.

A method for synthesis of compounds of Formula (I), illustrated inScheme 1, relies upon reaction of a 3-aminopropylphosphinic acid analogof Formula (II) with a 1-(acyloxy)-alkyl N-hydroxysuccinimidyl carbonatecompound of Formula (III), optionally in the presence of a base, asdescribed in the co-pending application Gallop et al., InternationalPublication No. WO 2005/066122 entitled “Synthesis of AcyloxyalkylCarbamate Prodrugs and Intermediates Thereof,” filed Dec. 30, 2004.

wherein:

R⁹ and R¹⁰ is chosen from hydrogen, acylamino, acyloxy,alkoxycarbonylamino, alkoxycarbonyloxy, alkyl, substituted alkyl,alkoxy, substituted alkoxy, aryl, substituted aryl, arylalkyl,carbamoyloxy, dialkylamino, heteroaryl, hydroxy, and sulfonamido, or R⁹and R¹⁰ together with the atoms to which they are bonded form asubstituted cycloalkyl, substituted cycloheteroalkyl, or substitutedaryl ring; and

R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ are as previously defined.

In certain embodiments of the method described in Scheme 1 forsynthesizing a compound of Formula (I), R² and R³ in the compound ofFormula (III) are different, such that the carbon atom to which thesesubstituents are bonded is a stereogenic center. In certain embodimentsof the method for synthesizing a compound of Formula (I), R² and R³ inthe compound of Formula (I) are different and the compound of Formula(I) is substantially one diastereomer.

In certain embodiments of the method described in Scheme 1 forsynthesizing a compound of Formula (I), R⁹ and R¹⁰ in the compound ofFormula (III) are each benzoyloxy, the stereochemistry at the carbon towhich R⁹ is bonded is of the R-configuration, and the stereochemistry atthe carbon to which R¹⁰ is bonded is of the R-configuration. In certainembodiments of the method described in Scheme 1 for synthesizing acompound of Formula (I), R⁹ and R¹⁰ in the compound of Formula (III) areeach benzoyloxy, the stereochemistry at the carbon to which R⁹ is bondedis of the S-configuration and the stereochemistry at the carbon to whichR¹⁰ is bonded is of the S-configuration.

In certain embodiments, the method of Scheme 1 is carried out in asolvent. Useful solvents include, but are not limited to, acetone,acetonitrile, dichloromethane, dichloroethane, chloroform, toluene,tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide,N-methylpyrrolidinone, dimethyl sulfoxide, pyridine, ethyl acetate,methyl tert-butyl ether, methanol, ethanol, isopropanol, tert-butanol,water, or combinations thereof. In certain embodiments, the solvent isacetone, acetonitrile, dichloromethane, toluene, tetrahydrofuran,pyridine, methyl tert-butyl ether, methanol, ethanol, isopropanol,water, or combinations thereof. In certain embodiments, the solvent is amixture of acetonitrile and water. In certain embodiments, the solventis a mixture of acetonitrile and water, with a volume ratio ofacetonitrile to water from about 1:5 to about 5:1. In certainembodiments, the solvent is a mixture of tetrahydrofuran and water, witha volume ratio of tetrahydrofuran to water from about 20:1 to about 2:1.In certain embodiments, the solvent is a mixture of methyl tert-butylether and water. In certain embodiments, the solvent is a mixture ofmethyl tert-butyl ether and water, with a volume ratio of methyltert-butyl ether to water from about 20:1 to about 2:1. In certainembodiments, the solvent is a mixture of methyl tert-butyl ether andwater, wherein the methyl tert-butyl ether contains from about 10% toabout 50% acetone by volume. In certain embodiments, the solvent isdichloromethane, water, or a combination thereof. In certainembodiments, the solvent is a biphasic mixture of dichloromethane andwater. In certain embodiments, the solvent is a biphasic mixture ofdichloromethane and water containing from about 0.001 equivalents toabout 0.1 equivalents of a phase transfer catalyst. In certainembodiments, the phase transfer catalyst is a tetraalkylammonium salt,and in certain embodiments, the phase transfer catalyst is atetrabutylammonium salt.

The method of Scheme 1 may be carried out at a temperature from about−20° C. to about 40° C. In certain embodiments, the temperature is fromabout −20° C. to about 25° C. In certain embodiments, the temperature isfrom about 0° C. to about 25° C. In certain embodiments, the temperatureis from about 25° C. to about 40° C.

In certain embodiments of the method of Scheme 1, the reaction isperformed in the absence of a base.

In other embodiments of the method of Scheme 1, the reaction isperformed in the presence of an inorganic base. In certain embodiments,the reaction is performed in the presence of an alkali metal bicarbonateor alkali metal carbonate salt. In other embodiments, the reaction isperformed in the presence of sodium bicarbonate.

In certain embodiments of the method of Scheme 1, the reaction isperformed in the presence of an organic base. In certain embodiments,the reaction is performed in the presence of triethylamine,tributylamine, diisopropylethylamine, dimethylisopropylamine,N-methylmorpholine, N-methylpyrrolidine, N-methylpiperidine, pyridine,2-methylpyridine, 2,6-dimethylpyridine, 4-dimethylaminopyridine,1,4-diazabicyclo[2.2.2]octane, 1, 8-diazabicyclo[5.4.0]undec-7-ene, or1,5-diazabicyclo[4.3.0]undec-7-ene, and in certain embodiments, thereaction is performed in the presence of triethylamine,diisopropylethylamine, N-methylmorpholine, or pyridine.

Pharmaceutical Compositions

Pharmaceutical compositions comprising a therapeutically effectiveamount of one or more 3-aminopropylphosphinic acid analog prodrugcompounds of Formula (I), in certain embodiments, in purified form,together with a suitable amount of a pharmaceutically acceptablevehicle, so as to provide a form for proper administration to a patientare provided herein. Suitable pharmaceutical vehicles include excipientssuch as starch, glucose, lactose, sucrose, gelatin, malt, rice, flour,chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodiumchloride, dried skim milk, glycerol, propylene, glycol, water, ethanol,and the like. The present compositions, if desired, may also containminor amounts of wetting or emulsifying agents, or pH buffering agents.In addition, auxiliary, stabilizing, thickening, lubricating, andcoloring agents may be used.

Pharmaceutical compositions may be manufactured by means of conventionalmixing, dissolving, granulating, dragee-making, levigating, emulsifying,encapsulating, entrapping, or lyophilizing processes. Pharmaceuticalcompositions may be formulated in conventional manner using one or morephysiologically acceptable carriers, diluents, excipients, orauxiliaries, which facilitate processing of compounds disclosed hereininto preparations, which may be used pharmaceutically. Properformulation is dependent upon the route of administration chosen.

Pharmaceutical compositions may take the form of solutions, suspensions,emulsion, tablets, pills, pellets, capsules, capsules containingliquids, powders, sustained-release formulations, suppositories,emulsions, aerosols, sprays, suspensions, or any other form suitable foruse. In certain embodiments, the pharmaceutically acceptable vehicle isa capsule (see e.g., Grosswald et al., U.S. Pat. No. 5,698,155). Otherexamples of suitable pharmaceutical vehicles have been described in theart (see Remington's Pharmaceutical Sciences, Philadelphia College ofPharmacy and Science, 19th Edition, 1995). In certain embodiments,compositions are formulated for oral delivery, particularly for oralsustained release administration.

Pharmaceutical compositions for oral delivery may be in the form oftablets, lozenges, aqueous or oily suspensions, granules, powders,emulsions, capsules, syrups, or elixirs, for example. Orallyadministered compositions may comprise one or more optional agents, forexample, sweetening agents such as fructose, aspartame, and saccharin;flavoring agents such as peppermint, oil of wintergreen, and cherry;coloring agents; and preserving agents, to provide a pharmaceuticallypalatable preparation. Moreover, when in tablet or pill form, thecompositions may be coated to delay disintegration and absorption in thegastrointestinal tract, thereby providing a sustained action over anextended period of time. Oral compositions may include standard vehiclessuch as mannitol, lactose, starch, magnesium stearate, sodiumsaccharine, cellulose, magnesium carbonate, etc. Such vehicles may be ofpharmaceutical grade.

For oral liquid preparations such as, for example, suspensions, elixirsand solutions, suitable carriers, excipients or diluents include water,saline, alkyleneglycols (e.g., propylene glycol), polyalkylene glycols(e.g., polyethylene glycol), oils, alcohols, slightly acidic buffershaving a pH ranging from about pH 4 to about pH 6 (e.g., acetate,citrate, ascorbate at between about 5 mM to about 50 mM), etc.Additionally, flavoring agents, preservatives, coloring agents, bilesalts, acylcarnitines, and the like may be added.

When the compounds of Formula (I) are acidic, they may be included inany of the above-described formulations as free acids, pharmaceuticallyacceptable salts, solvates, or hydrates. Pharmaceutically acceptablesalts substantially retaining the activity of the free acid forms may beprepared by reaction with bases, and tend to be more soluble in aqueousand other protic solvents than the corresponding free acid forms. Incertain embodiments, sodium salts of a compound of Formula (I) are usedin the above described formulations.

Sustained Release Oral Dosage Forms

The disclosed compounds may be used with a number of different dosageforms, which may be adapted to provide sustained release of a compoundof Formula (I) upon oral administration.

In certain embodiments, dosage forms comprise beads, which ondissolution or diffusion release a compound of Formula (I) over anextended period of hours, in certain embodiments over a period of atleast about 6 hours, and in certain embodiments, over a period of atleast about 8 hours and in certain embodiments, over a period of atleast about 12 hours. The beads may have a central composition or corecomprising a compound disclosed herein and pharmaceutically acceptablevehicles, including an optional lubricant, antioxidant, and buffer. Thebeads may be medical preparations with a diameter of about 0.05 mm toabout 2 mm. Individual beads may comprise doses of a compound of Formula(I), for example, doses of up to about 40 mg of compound. The beads, incertain embodiments, are formed of non-cross-linked materials to enhancetheir discharge from the gastrointestinal tract. The beads may be coatedwith a release rate-controlling polymer that gives a timed-releaseprofile.

The time-release beads may be manufactured into a tablet fortherapeutically effective administration. The beads may be made intomatrix tablets by the direct compression of a plurality of beads coatedwith, for example, an acrylic resin and blended with excipients such ashydroxypropylmethyl cellulose. The manufacture of beads is disclosed inthe art (Lu, Int. J. Pharm. 1994, 112, 117-124; Pharmaceutical Sciencesby Remington, 14^(th) ed, pp. 1626-1628 (1970); Fincher, J. Pharm. Sci.1968, 57, 1825-1835; and U.S. Pat. No. 4,083,949), as has themanufacture of tablets (Pharmaceutical Sciences, by Remington, 17^(th)Ed, Ch. 90, pp. 1603-1625 (1985)).

One type of sustained release oral dosage formulation that may be usedwith the compounds of Formula (I) comprises an inert core, such as asugar sphere, coated with an inner drug-containing layer and an outermembrane layer controlling drug release from the inner layer. A sealcoatmay be provided between the inert core and the layer containing theactive ingredient. When the core is of a water-soluble orwater-swellable inert material, the sealcoat may be in the form of arelatively thick layer of a water-insoluble polymer. Such a controlledrelease beads may thus comprise: (i) a core unit of a substantiallywater-soluble or water-swellable inert material; (ii) a first layer onthe core unit of a substantially water-insoluble polymer; (iii) a secondlayer covering the first layer and containing an active ingredient; and(iv) a third layer on the second layer of polymer effective forcontrolled release of the active ingredient, wherein the first layer isadapted to control water penetration into the core.

In certain embodiments, the first layer (ii) above constitutes more thanabout 2% (w/w) of the final bead composition, such as more than about 3%(w/w), e.g., from about 3% to about 80% (w/w). The amount of the secondlayer (ii) above usually constitutes from about 0.05% to about 60%(w/w), such as from about 0.1% to about 30% (w/w) of the final beadcomposition. The amount of the third layer (iv) above usuallyconstitutes from about 1% to about 50% (w/w), for example, from about 2%to about 25% (w/w) of the final bead composition. The core unit may havea size from about 0.05 to about 2 mm. The controlled release beads maybe provided in a multiple unit formulation, such as a capsule or atablet.

The cores may be of a water-soluble or swellable material and may be anysuch material that is conventionally used as cores or any otherpharmaceutically acceptable water-soluble or water-swellable materialmade into beads or pellets. The cores may be spheres of materials suchas sucrose/starch (Sugar Spheres NF), sucrose crystals, or extruded anddried spheres typically comprising excipients such as microcrystallinecellulose and lactose. The substantially water-insoluble material in thefirst, or sealcoat layer is generally a “GI insoluble” or “GI partiallyinsoluble” film forming polymer (dispersed or dissolved in a solvent).Examples include, but are not limited to, ethyl cellulose, celluloseacetate, and cellulose acetate butyrate, polymethacrylates such as ethylacrylate/methyl methacrylate copolymer (Eudragit NE-30-D), ammoniomethacrylate copolymer types A and B (Eudragit RL30D and RS30D), andsilicone elastomers. A plasticizer is used together with the polymer.Exemplary plasticizers include, but are not limited to, dibutylsebacate,propylene glycol, triethylcitrate, tributylcitrate, castor oil,acetylated monoglycerides, acetyl triethylcitrate, acetyl butylcitrate,diethyl phthalate, dibutyl phthalate, triacetin, and fractionatedcoconut oil (medium-chain triglycerides). The second layer containingthe active ingredient may comprise the active ingredient with or withouta polymer as a binder. The binder, when used, may be hydrophilic but maybe water-soluble or water-insoluble. Examples of polymers that may beused in the second layer containing the active drug are hydrophilicpolymers such as, for example, polyvinylpyrrolidone (PVP), polyalkyleneglycol such as polyethylene glycol, gelatine, polyvinyl alcohol, starch,and derivatives thereof, cellulose derivatives, such ashydroxypropylmethyl cellulose (HPMC), hydroxypropyl cellulose,carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethylcellulose, carboxyethyl cellulose, and carboxymethylhydroxyethylcellulose, acrylic acid polymers, polymethacrylates, and any otherappropriate pharmaceutically acceptable polymer. The ratio of drug tohydrophilic polymer in the second layer is usually in the range of fromabout 1:100 to about 100:1 (w/w). Suitable polymers for use in the thirdlayer, or membrane, for controlling the drug release may be chosen fromwater-insoluble polymers or polymers with pH-dependent solubility, suchas, for example, ethyl cellulose, hydroxypropylmethyl cellulosephthalate, cellulose acetate phthalate, cellulose acetate trimellitate,polymethacrylates, or combinations thereof, optionally combined withplasticizers, such as those mentioned above. Optionally, a controlledrelease layer comprises, in addition to the polymers above, othersubstance(s) with different solubility characteristics, to adjust thepermeability and thereby the release rate, of the controlled releaselayer. Examples of polymers that may be used as a modifier togetherwith, for example, ethyl cellulose include, but are not limited to,HPMC, hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose,carboxymethylcellulose, polyethylene glycol, polyvinylpyrrolidone (PVP),polyvinyl alcohol, polymers with pH-dependent solubility, such ascellulose acetate phthalate or ammonio methacrylate copolymer andmethacrylic acid copolymer, and combinations thereof. Additives such assucrose, lactose and pharmaceutical grade surfactants may also beincluded in the controlled release layer, if desired.

The preparation of the multiple unit formulation may comprise theadditional step of transforming the prepared beads into a pharmaceuticalformulation, such as by filling a predetermined amount of the beads intoa capsule, or compressing the beads into tablets. Examples ofmulti-particulate sustained release oral dosage forms are described in,for example, U.S. Pat. Nos. 6,627,223 and 5,229,135.

In certain embodiments, an oral sustained release pump may be used (seeLanger, supra; Sefton, CRC Crit Ref Biomed. Eng. 1987, 14, 201; Saudeket al., N. Engl. J Med. 1989, 321, 574).

In certain embodiments, polymeric materials may be used (see “MedicalApplications of Controlled Release,” Langer and Wise (eds.), CRC Press.,Boca Raton, Fla. (1974); “Controlled Drug Bioavailability,” Drug ProductDesign and Performance, Smolen and Ball (eds.), Wiley, New York (1984);Langer et al., J Macromol. Sci. Rev. Macromol Chem. 1983, 23, 61; seealso Levy et al., Science 1985, 228, 190; During et al., Ann. Neurol.1989, 25, 351; Howard et al., J. Neurosurg. 1989, 71, 105). In certainembodiments, polymeric materials may be used for oral sustained releasedelivery. Polymers include, but are not limited to, sodiumcarboxymethylcellulose, hydroxypropylcellulose,hydroxypropylmethylcellulose, and hydroxyethylcellulose (especially,hydroxypropylmethylcellulose). Other cellulose ethers are described(Alderman, Int. J. Pharm. Tech. & Prod. Mfr. 1984, 5(3), 1-9). Factorsaffecting drug release are well known to the skilled artisan and aredescribed in the art (Bamba et al., Int. J. Pharm. 1979, 2, 307).

In certain embodiments, enteric-coated preparations may be used for oralsustained release administration. Examples of coating materials includepolymers with a pH-dependent solubility (i.e., pH-controlled release),polymers with a slow or pH-dependent rate of swelling, dissolution orerosion (i.e., time-controlled release), polymers that are degraded byenzymes (i.e., enzyme-controlled release), and polymers that form firmlayers that are destroyed by an increase in pressure (i.e.,pressure-controlled release).

In certain embodiments, drug-releasing lipid matrices may be used fororal sustained release administration. An example is solidmicroparticles of a compound of Formula (I) coated with a thincontrolled release layer of a lipid (e.g., glyceryl behenate and/orglyceryl palmitostearate) as disclosed in Farah et al., U.S. Pat. No.6,375,987 and Joachim et al., U.S. Pat. No. 6,379,700. The lipid-coatedparticles may optionally be compressed to form a tablet. Anothercontrolled release lipid-based matrix material that is suitable forsustained release oral administration comprises polyglycolizedglycerides as disclosed in Roussin et al., U.S. Pat. No. 6,171,615.

In certain embodiments, waxes may be used for oral sustained releaseadministration. Examples of suitable sustained compound-releasing waxesare disclosed in Cain et al., U.S. Pat. No. 3,402,240 (carnauba wax,candelilla wax, esparto wax, and ouricury wax); Shtohryn et al., U.S.Pat. No. 4,820,523 (hydrogenated vegetable oil, bees wax, carnauba wax,paraffin, candelilla, ozokerite, and combinations thereof); and Walters,U.S. Pat. No. 4,421,736 (combination of paraffin and castor wax).

In certain embodiments, osmotic delivery systems may be used for oralsustained release administration (Verma et al., Drug Dev. Ind. Pharm.2000, 26, 695-708). In certain embodiments, OROS® systems made by AlzaCorporation, Mountain View, Calif. may be used for oral sustainedrelease delivery devices (Theeuwes et al., U.S. Pat. No. 3,845,770;Theeuwes et al., U.S. Pat. No. 3,916,899).

In certain embodiments, a controlled-release system may be placed inproximity of the target of a compound disclosed herein (e.g., within thespinal cord), thus requiring only a fraction of the systemic dose (seee.g., Goodson, in “Medical Applications of Controlled Release,” supra,vol. 2, pp. 115-138 (1984)). Other controlled-release systems discussedin Langer, Science 1990, 249, 1527-1533, may also be used.

In certain embodiments, dosage forms comprise a compound of Formula (I)coated on a polymer substrate. The polymer may be an erodible, or anonerodible polymer. The coated substrate may be folded onto itself toprovide a bilayer polymer drug dosage form. For example, a compounddisclosed of Formula (I) gelatin, polyvinyl alcohol, polyorthoester,polyacetyl, or a polyorthocarbonate and the coated polymer folded ontoitself to provide a bilaminated dosage form. In operation, thebioerodible dosage form erodes at a controlled rate to dispense acompound of Formula (I) over a sustained release period. Examples ofuseful biodegradable polymers include biodegradable poly(amides),poly(amino acids), poly(esters), poly(lactic acid), poly(glycolic acid),poly(carbohydrate), poly(orthoester), poly (orthocarbonate),poly(acetyl), poly(anhydrides), biodegradable poly(dihydropyrans), andpoly(dioxinones), which are known in the art (Rosoff, Controlled Releaseof Drugs Chap. 2, pp. 53-95 (1989); and in U.S. Pat. Nos. 3,811,444,3,962,414, 4,066,747, 4,070,347, 4,079,038, and 4,093,709).

In certain embodiments, dosage forms comprise a compound of Formula (I)loaded into a polymer that releases the compound by diffusion through apolymer, or by flux through pores or by rupture of a polymer matrix.Drug delivery polymeric dosage forms comprise between about 2 mg toabout 500 mg of compound homogenously contained in or on a polymer. Thedosage forms comprise at least one exposed surface at the beginning ofdose delivery. The non-exposed surface, when present, is coated with apharmaceutically acceptable material impermeable to the passage of acompound. The dosage forms may be manufactured by procedures known inthe art. An example of providing the dosage forms comprise blending apharmaceutically acceptable carrier like polyethylene glycol, with aknown dose of a compound at an elevated temperature, (e.g., about 37°C.), and adding it to a silastic medical grade elastomer with across-linking agent, for example, octanoate, followed by casting in amold. The step is repeated for each optional successive layer. Thesystem is allowed to set for about 1 hour, to provide the dosage form.Representative polymers for manufacturing the dosage form are chosenfrom olefinic polymers, vinyl polymers, addition polymers, condensationpolymers, carbohydrate polymer and silicone polymers such aspolyethylene, polypropylene, polyvinyl acetate, polymethylacrylate,polyisobutylmethacrylate, poly alginate, polyamide, and polysilicone.The polymers and procedures for manufacturing the polymers are describedin the art (Coleman et al., Polymers 1990, 31, 1187-1231; Roerdink etal., Drug Carrier Systems 1989, 9, 57-10; Leong et al., Adv. DrugDelivery Rev. 1987, 1, 199-233; Roff et al., Handbook of Common Polymers1971, CRC Press; and U.S. Pat. No. 3,992,518).

In certain embodiments, dosage forms comprise a plurality of pills. Thetime-release pills provide a number of individual doses for providingvarious time doses for achieving a sustained-release prodrug deliveryprofile over an extended period of time up to about 24 hours. The matrixcomprises a hydrophilic polymer chosen from, for example, apolysaccharide, agar, agarose, natural gum, alkali alginate includingsodium alginate, carrageenan, fucoidan, furcellaran, laminaran, hypnea,gum arabic, gum ghatti, gum karaya, gum tragacanth, locust bean gum,pectin, amylopectin, gelatin, and a hydrophilic colloid. The hydrophilicmatrix comprises a plurality of about 4 to about 50 pills, each pillcomprises a dose population of from about 10 ng, about 0.5 mg, about 1mg, about 1.2 mg, about 1.4 mg, about 1.6 mg, about 5.0 mg, etc. Thepills comprise a release rate-controlling wall of about 0.001 mm up toabout 10 mm thickness to provide for the timed release of a compound.Examples of wall forming materials include a triglyceryl ester chosenfrom glyceryl tristearate, glyceryl monostearate, glyceryl dipalmitate,glyceryl laureate, glyceryl didecenoate, and glyceryl tridenoate. Otherwall forming materials include polyvinyl acetate, phthalate,methylcellulose phthalate, and microporous olefins. Procedures formanufacturing pills are disclosed in U.S. Pat. Nos. 4,434,153,4,721,613, 4,853,229, 2,996,431, 3,139,383, and 4,752,470.

In certain embodiments, dosage forms comprise an osmotic dosage form,which comprises a semipermeable wall that surrounds a therapeuticcomposition comprising the compound. In use within a patient, theosmotic dosage form comprising a homogenous composition, imbibes fluidthrough the semipermeable wall into the dosage form in response to theconcentration gradient across the semipermeable wall. The therapeuticcomposition in the dosage form develops osmotic pressure differentialthat causes the therapeutic composition to be administered through anexit from the dosage form over a prolonged period of time up to about 24hours (or even in some cases up to about 30 hours) to provide controlledand sustained compound release. These delivery platforms may provide anessentially zero order delivery profile as opposed to the spikedprofiles of immediate release formulations.

In certain embodiments, a dosage form comprises another osmotic dosageform comprising a wall surrounding a compartment, the wall comprising asemipermeable polymeric composition permeable to the passage of fluidand substantially impermeable to the passage of compound present in thecompartment, a compound-containing layer composition in the compartment,a hydrogel push layer composition in the compartment comprising anosmotic formulation for imbibing and absorbing fluid for expanding insize for pushing the compound composition layer from the dosage form,and at least one passageway in the wall for releasing the prodrugcomposition. The method delivers the compound by imbibing fluid throughthe semipermeable wall at a fluid imbibing rate determined by thepermeability of the semipermeable wall and the osmotic pressure acrossthe semipermeable wall causing the push layer to expand, therebydelivering the compound from the dosage form through the exit passagewayto a patient over a prolonged period of time (up to about 24 or evenabout 30 hours). The hydrogel layer composition may comprise about 10 mgto about 1000 mg of a hydrogel such as a member chosen from apolyalkylene oxide of about 1,000,000 to about 8,000,000 weight-averagemolecular weight, which are chosen from a polyethylene oxide of about1,000,000 weight-average molecular weight, a polyethylene oxide of about2,000,000 molecular weight, a polyethylene oxide of about 4,000,000molecular weight, a polyethylene oxide of about 5,000,000 molecularweight, a polyethylene oxide of about 7,000,000 molecular weight, and apolypropylene oxide of the about 1,000,000 to about 8,000,000weight-average molecular weight; or about 10 mg to about 1000 mg of analkali carboxymethylcellulose of about 10,000 to about 6,000,000 weightaverage molecular weight, such as sodium carboxymethylcellulose orpotassium carboxymethylcellulose. The hydrogel expansion layer comprisesabout 0.0 mg to about 350 mg, in present manufacture; about 0.1 mg toabout 250 mg of a hydroxyalkylcellulose of about 7,500 to about 4,500,00weight-average molecular weight (e.g., hydroxymethylcellulose,hydroxyethylcellulose, hydroxypropylcellulose, hydroxybutylcellulose, orhydroxypentylcellulose) in present manufacture; about 1 mg to about 50mg of an agent chosen from sodium chloride, potassium chloride,potassium acid phosphate, tartaric acid, citric acid, raffinose,magnesium sulfate, magnesium chloride, urea, inositol, sucrose, glucose,and sorbitol; about 0 to about 5 mg of a colorant, such as ferric oxide;about 0 mg to about 30 mg, in a present manufacture, about 0.1 mg toabout 30 mg of a hydroxypropylalkylcellulose of about 9,000 to about225,000 average-number molecular weight, chosen fromhydroxypropylethylcellulose, hydroxypropypentylcellulose,hydroxypropylmethylcellulose, and hydropropylbutylcellulose; about 0.00to about 1.5 mg of an antioxidant chosen from ascorbic acid, butylatedhydroxyanisole, butylated hydroxyquinone, butylhydroxyanisol,hydroxycoumarin, butylated hydroxytoluene, cephalm, ethyl gallate,propyl gallate, octyl gallate, lauryl gallate, propyl-hydroxybenzoate,trihydroxybutylrophenone, dimethylphenol, dibutylphenol, vitamin E,lecithin, and ethanolamine; and about 0.0 mg to about 7 mg of alubricant chosen from calcium stearate, magnesium stearate, zincstearate, magnesium oleate, calcium palmitate, sodium suberate,potassium laurate, salts of fatty acids, salts of alicyclic acids, saltsof aromatic acids, stearic acid, oleic acid, palmitic acid, a mixture ofa salt of a fatty, alicyclic, or aromatic acid, and a fatty, alicyclic,or aromatic acid.

In osmotic dosage forms, the semipermeable wall comprises a compositionthat is permeable to the passage of fluid and impermeable to the passageof prodrug. The wall is nontoxic and comprises a polymer chosen from acellulose acylate, cellulose diacylate, cellulose triacylate, celluloseacetate, cellulose diacetate, and cellulose triacetate. The wallcomprises about 75 wt % (weight percent) to about 100 wt % of thecellulosic wall-forming polymer or, the wall may comprise additionallyabout 0.01 wt % to about 80 wt % of polyethylene glycol, or about 1 wt %to about 25 wt % of a cellulose ether chosen from hydroxypropylcelluloseor a hydroxypropylalkycellulose such as hydroxypropylmethylcellulose.The total weight percent of all components comprising the wall is equalto about 100 wt %. The internal compartment comprises thecompound-containing composition alone or in layered position with anexpandable hydrogel composition. The expandable hydrogel composition inthe compartment increases in dimension by imbibing the fluid through thesemipermeable wall, causing the hydrogel to expand and occupy space inthe compartment, whereby the drug composition is pushed from the dosageform. The therapeutic layer and the expandable layer act together duringthe operation of the dosage form for the release of prodrug to a patientover time. The dosage form comprises a passageway in the wall thatconnects the exterior of the dosage form with the internal compartment.The osmotic powered dosage form may be made to deliver prodrug from thedosage form to the patient at a zero order rate of release over a periodof up to about 24 hours.

The expression “passageway” as used herein comprises means and methodssuitable for the metered release of the compound from the compartment ofthe dosage form. The exit means comprises at least one passageway,including orifice, bore, aperture, pore, porous element, hollow fiber,capillary tube, channel, porous overlay, or porous element that providesfor the osmotic controlled release of compound. The passageway includesa material that erodes or is leached from the wall in a fluidenvironment of use to produce at least one controlled-releasedimensioned passageway. Examples of materials suitable for forming apassageway, or a multiplicity of passageways comprise a leachablepoly(glycolic) acid or poly(lactic) acid polymer in the wall, agelatinous filament, poly(vinyl alcohol), leach-able polysaccharides,salts, and oxides. A pore passageway, or more than one pore passageway,may be formed by leaching a leachable compound, such as sorbitol, fromthe wall. The passageway possesses controlled-release dimensions, suchas round, triangular, square and elliptical, for the metered release ofprodrug from the dosage form. The dosage form may be constructed withone or more passageways in spaced apart relationship on a single surfaceor on more than one surface of the wall. The expression “fluidenvironment” denotes an aqueous or biological fluid as in a humanpatient, including the gastrointestinal tract. Passageways and equipmentfor forming passageways are disclosed in U.S. Pat. Nos. 3,845,770,3,916,899, 4,063,064, 4,088,864, and 4,816,263. Passageways formed byleaching are disclosed in U.S. Pat. Nos. 4,200,098 and 4,285,987.

Regardless of the specific form of sustained release oral dosage formused, compounds may be released from the dosage form over a period of atleast about 6 hours, in certain embodiments, over a period of at leastabout 8 hours, and in certain embodiments, over a period of at leastabout 12 hours. Further, the dosage form may release from about 0 toabout 30% of the prodrug in about 0 to about 2 hours, from about 20 toabout 50% of the prodrug in about 2 to about 12 hours, from about 50 toabout 85% of the prodrug in about 3 to about 20 hours, and greater thanabout 75% of the prodrug in about 5 to about 18 hours. The sustainedrelease oral dosage form further provides a concentration of the3-aminopropylphosphinic acid analog in the blood plasma of the patientover time, which curve has an area under the curve (AUC) that isproportional to the dose of the prodrug of the 3-aminopropylphosphinicacid analog administered, and a maximum concentration C_(max). TheC_(max) may be less than about 75%, and in certain embodiments, lessthan about 60%, of the C_(max) obtained from administering an equivalentdose of the compound from an immediate release oral dosage form and theAUC is substantially the same as the AUC obtained from administering anequivalent dose of the prodrug from an immediate release oral dosageform.

In certain embodiments, a pharmaceutical composition or dosage formcomprising a compound of Formula (I) is capable of maintaining atherapeutically effective concentration of a compound of Formula (I) inthe plasma of a patient for at least about 4 hours, in certainembodiments for at least about 8 hours, and in certain embodiments forat least about 12 hours, after the pharmaceutical composition or dosageform is orally administered to the patient. In certain embodiments, apharmaceutical composition or dosage form comprising a compound ofFormula (I) is capable of maintaining a therapeutically effectiveconcentration of the corresponding 3-aminopropylphosphinc acid or analogthereof of a compound of Formula (I) in the plasma of a patient for atleast about 4 hours, in certain embodiments for at least about 8 hours,and in certain embodiments for at least about 12 hours, after thepharmaceutical composition or dosage form is orally administered to thepatient. In certain embodiments, dosage forms may be administered once,twice, three times, or four times per day.

Therapeutic Uses of Compounds and Compositions

In certain embodiments, a therapeutically effective amount of one ormore compounds of Formula (I) may be administered to a patient, such asa human, suffering from cognitive or memory disorders including MildCognitive Impairment (MCI) and cognitive impairment associated withAlzheimer's disease. In certain embodiments, a therapeutically effectiveamount of one or more compounds of Formula (I) may be administered to apatient, such as a human, suffering from a mood disorder such asdepression or anxiety. In certain embodiments, a therapeuticallyeffective amount of one or more compounds of Formula (I) may beadministered to a patient, such as a human, suffering from a motiondisorder such as epilepsy, particularly “petit-mal” type epilepsyincluding spontaneous absence epilepsy and atypical absence epilepsy. Incertain of the above embodiments, sustained release oral dosage formsare administered to the patients.

When used to treat the diseases or disorders disclosed herein thetherapeutically effective amount of one or more compounds of Formula (I)may be administered or applied singly or in combination with otheragents. The therapeutically effective amount of one or more compounds ofFormula (I) may be capable of delivering a compound disclosed herein incombination with another pharmaceutically active agent, includinganother compound disclosed herein.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat mood disorders such as depression, or moreparticularly, depressive disorders, for example, single episodic orrecurrent major depressive disorders, dysthymic disorders, depressiveneurosis and neurotic depression, melancholic depression, includinganorexia, weight loss, insomnia, early morning waking and psychomotorretardation, atypical depression or reactive depression, includingincreased appetite, hypersomnia, psychomotor agitation or irritability,seasonal affective disorder and pediatric depression; bipolar disordersor manic depression, such as bipolar I disorder, bipolar II disorder,and cyclothymic disorder; conduct disorder and disruptive behaviordisorder; anxiety disorders, such as panic disorder with or withoutagoraphobia, agoraphobia without history of panic disorder, specificphobias, for example, specific animal phobias, social anxiety, socialphobia, obsessive-compulsive disorder, stress disorders, includingpost-traumatic stress disorder and acute stress disorder, andgeneralized anxiety disorders; borderline personality disorder;schizophrenia and other psychotic disorders, for example,schizophreniform disorders, schizoaffective disorders, delusionaldisorders, brief psychotic disorders, shared psychotic disorders,psychotic disorders with delusions or hallucinations, psychotic episodesof anxiety, anxiety associated with psychosis, psychotic mood disorderssuch as severe major depressive disorder; mood disorders associated withpsychotic disorders such as acute mania and depression associated withbipolar disorder, mood disorders associated with schizophrenia; andbehavioral disturbances associated with mental retardation, autisticdisorder, and conduct disorder.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat delirium, dementia, and amnestic and othercognitive or neurodegenerative disorders, such as Parkinson's disease,Huntington's disease, Alzheimer's disease, senile dementia, dementia ofthe Alzheimer's type, memory disorders including Mild CognitiveImpairment such as occurring after a stroke, in Alzheimer's disease, indelirium, in dementia, or in schizophrenia, loss of executive function,vascular dementia, and other dementias, for example, due to HIV disease,head trauma, Parkinson's disease, Huntington's disease, Pick's disease,Friedrich's disease, Creutzfeldt-Jakob disease, or due to multipleetiologies.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat movement disorders such as akinesias,dyskinesias, including familial paroxysmal dyskinesias, spasticities,Scott syndrome, hiccups, chorea and athetosis, coordination disorderssuch as Friedrich's ataxia and ataxia-telangiectasia, dystonia includingidiopathic torsion dystonia, blepharospasm, spasmodic torticollis,spasmodic dysphonia, yips, and spasmodic torticollis, Huntington'sdisease, myoclonus, Parkinson's disease, supranuclear palsy, Shy-Dragersyndrome, tics including Tourette's syndrome, tremor, and akinetic-rigidsyndrome; extra-pyramidal movement disorders such as medication-inducedmovement disorders, for example, neuroleptic-induced Parkinsonism,neuroleptic malignant syndrome, neuroleptic-induced acute dystonia,neuroleptic-induced acute akathisia, neuroleptic-induced tardivedyskinesia and medication-induced postural tremor.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat chemical dependencies and addictions (e.g.,dependencies on, or addictions to, alcohol, heroin, cocaine,benzodiazepines, nicotine, or phenobarbitol) and behavioral addictionssuch as an addiction to gambling; and ocular disorders such as glaucomaand ischemic retinopathy.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used as an anti-convulsive to treat seizures such asepileptic seizure. Methods for treating convulsions compriseadministering a therapeutically effective amount of a3-aminopropylphosphinic acid analog prodrug of Formula (I) to a patientin need of such treatment. In certain embodiments,3-aminopropylphosphinic acid analog prodrugs of Formula (I) may beadministered orally to treat convulsions and/or seizures. In certainembodiments, 3-aminopropylphosphinic acid analog prodrugs of Formula (I)may be parenterally administered to treat convulsions and/or seizures.In certain embodiments, 3-aminopropylphosphinic acid analog prodrugs ofFormula (I) may be administered in amounts from about 100 mg to about 4g daily to treat convulsions and/or seizures.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used as anti-depressants to treat mood disorders such asdepression. Methods for treating depression comprise administering atherapeutically effective amount of a 3-aminopropylphosphinic acidanalog prodrug of Formula (I) to a patient in need of such treatment. Incertain embodiments, 3-aminopropylphosphinic acid analog prodrugs ofFormula (I) may be administered orally to treat depression. In certainembodiments, 3-aminopropylphosphinic acid analog prodrugs of Formula (I)may be parenterally administered to treat depression. In certainembodiments, 3-aminopropylphosphinic acid analog prodrugs of Formula (I)may be administered in amounts from about 100 mg to about 4 g daily totreat depression.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat mood disorders such as anxiety. Methods fortreating anxiety comprise administering a therapeutically effectiveamount of 3-aminopropylphosphinic acid analog prodrugs of Formula (I) toa patient in need of such treatment. In certain embodiments, a3-aminopropylphosphinic acid analog prodrug of Formula (I) may beadministered orally to treat anxiety. In certain embodiments,3-aminopropylphosphinic acid analog prodrugs of Formula (I) may beparenterally administered to treat anxiety. In certain embodiments,3-aminopropylphosphinic acid analog prodrugs of Formula (I) may beadministered in amounts from about 100 mg to about 4 g daily to treatanxiety.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be used to treat cognitive or memory disorders such ascognitive memory impairment and/or cognitive impairment associated withAlzheimer's disease. Methods for treating cognitive memory impairmentcomprise administering a therapeutically effective amount of a3-aminopropylphosphinic acid analog prodrug of Formula (I) to a patientin need of such treatment. In certain embodiments,3-aminopropylphosphinic acid analog prodrugs of Formula (I) may beadministered orally to treat cognitive memory disorders. In certainembodiments, 3-aminopropylphosphinic acid analog prodrugs of Formula (I)may be parenterally administered to treat cognitive memory disorders. Incertain embodiments, 3-aminopropylphosphinic acid analog prodrugs ofFormula (I) may be administered in amounts from about 100 mg to about 4g daily to treat cognitive memory disorders.

When used to treat and diseases or disorders disclosed herein,3-aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, may be administered or applied singly, or in combination withother agents. The compounds and/or pharmaceutical compositionscomprising a compound of Formula (I) may also be administered or appliedsingly, or in combination with other pharmaceutically active agents.

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, and/or pharmaceutical compositions thereof may be administeredorally. 3-Aminopropylphosphinic acid analog prodrugs of Formula (I)and/or pharmaceutical compositions thereof may also be administered byany other convenient route, for example, by infusion or bolus injection,by absorption through epithelial or mucocutaneous linings (e.g., oralmucosa, rectal, and intestinal mucosa, etc.). Administration may besystemic or local. Various delivery systems are known, (e.g.,encapsulation in liposomes, microparticles, microcapsules, capsules,etc.) that may be used to administer a compound and/or pharmaceuticalcomposition. Methods of administration include, but are not limited to,intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous,intranasal, epidural, oral, sublingual, intranasal, intracerebral,intravaginal, transdermal, rectally, inhalation, or topically,particularly to the ears, nose, eyes, or skin.

In certain embodiments, it may be desirable to introduce3-aminopropylphosphinic acid analog prodrugs of Formula (I) and/orpharmaceutical compositions thereof into the central nervous system byany suitable route, including intraventricular, intrathecal, andepidural injection. Intraventricular injection may be facilitated by anintraventricular catheter, for example, attached to a reservoir, such asan Ommaya reservoir.

In certain embodiments, 3-aminopropylphosphinic acid analog prodrugs ofFormula (I) and/or pharmaceutical compositions thereof may be deliveredvia sustained release systems, may be oral sustained release systems. Inother embodiments, a pump may be used (Langer, supra; Sefton, 1987 CRCCrit Ref Biomed Eng. 14, 201; and Saudek et al., 1989 N. Engl. J Med.321, 574).

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) orpharmaceutically acceptable salts or solvates thereof as disclosedherein, and/or pharmaceutical compositions thereof may providetherapeutic or prophylactic levels of the corresponding3-aminopropylphosphinic acid analog upon in vivo administration to apatient. The prodrug promoiety of the compounds of Formula (I) may becleaved either chemically and/or enzymatically. One or more enzymespresent in the stomach, intestinal lumen, intestinal tissue, blood,liver, brain, or any other suitable tissue of a mammal may enzymaticallycleave the promoiety of the administered compounds.

The promoiety of a 3-aminopropylphosphinic acid analog prodrug ofFormula (I) may be cleaved prior to absorption by the gastrointestinaltract (e.g., within the stomach or intestinal lumen) and/or afterabsorption by the gastrointestinal tract (e.g., in intestinal tissue,blood, liver, or other suitable tissue of a mammal). In certainembodiments, the 3-aminopropylphosphinic acid analog remains conjugatedto the prodrug promoiety during transit across the intestinal mucosalbarrier to provide protection from presystemic metabolism. In certainembodiments, a 3-aminopropylphosphinic acid analog prodrugs of Formula(I) is essentially not metabolized to a 3-aminopropylphosphinic acidanalog within enterocytes but is metabolized to the parent drug withinthe systemic circulation. Cleavage of the promoiety of the3-aminopropylphosphinic acid analog prodrugs of Formula (I) afterabsorption by the gastrointestinal tract may allow these prodrugs to beabsorbed into the systemic circulation either by active transport,passive diffusion, or by a mixture of both active and passive processes.Accordingly, in certain embodiments, a pharmaceutical composition ordosage form of the present disclosure is capable of maintaining atherapeutically effective concentration of a 3-aminopropylphosphinicacid analog compound in the blood plasma of a patient for a period of atleast about 4 hours, in certain embodiments for a period of at leastabout 8 hours, and in certain embodiments for a period of at least about12 hours, after the pharmaceutical composition or dosage form comprisinga corresponding 3-aminopropylphosphinic acid analog prodrug of Formula(I) is orally administered to the patient.

In certain embodiments, prodrugs of 3-aminopropylphosphinic acid analogsprovided by the present disclosure can be useful in treating Alzheimer'sdisease and cognitive or memory disorders associated with Alzheimer'sdisease. Alzheimer's disease is a progressive loss of mental functioncharacterized by degeneration of brain tissue, including loss of nervecells and the development of senile plaques and neurofibrillary tangles.In Alzheimer's disease, parts of the brain degenerate, destroying nervecells and reducing the responsiveness of the maintaining neurons toneurotransmitters. Abnormalities in brain tissue consist of senile orneuritic plaques, e.g., clumps of dead nerve cells containing anabnormal, insoluble protein called amyloid, and neurofibrillary tangles,twisted strands of insoluble proteins in the nerve cell.

GABA_(B) antagonists are useful in the treatment of cognitive or memorydisorders including Mild Cognitive Impairment (MCI) and cognitiveimpairment associated with Alzheimer's disease (see e.g., Baylis et al.,U.S. Pat. No. 5,190,933; Pearlman et al., U.S. Application PublicationNo. 2002/0187977; Froestl et al., Biochem. Pharmacol. 2004, 68,1479-1487; Helm et al., Neuropharmacol. 2005, 48, 956-964; Mondadori etal., Behav. Brain Res. 1996, 77, 227-229; Mondadori et al., Behav.Neural Biol. 1993, 60, 62-68; and Nakagawa et al., Brain Res. 1997, 766,101-106).

The efficacy of administering a prodrug of a 3-aminopropylphosphinicacid analog provided by the present disclosure for treating Alzheimer'sdisease may be assessed using animal and human models of Alzheimer'sdisease and clinical studies. Useful animal models for assessing theefficacy of compounds for treating Alzheimer's disease are disclosed,for example, in Van Dam and De Dyn, Nature Revs Drug Disc 2006, 5,956-970; Simpkins et al., Ann N Y Acad Sci, 2005, 1052, 233-242; Higginsand Jacobsen, Behav Pharmacol 2003, 14(5-6), 419-38; Janus and Westaway,Physiol Behav 2001, 73(5), 873-86; Bardgett et al., Brain Res Bull 2003,60, 131-142; and Conn, ed., “Handbook of Models in Human Aging,” 2006,Elsevier Science & Technology.

In certain embodiments, compounds prodrugs of 3-aminopropylphosphinicacid analogs provided by the present disclosure and pharmaceuticalcompositions thereof can be used to treat a mood disorder such as, forexample, a bipolar disorder and a depressive disorder.

Bipolar disorder is a psychiatric condition characterized by periods ofextreme mood. The moods can occur on a spectrum ranging from depression(e.g., persistent feelings of sadness, anxiety, built, anger, isolation,and/or hopelessness, disturbances in sleep and appetite, fatigue andloss of interest in usually enjoyed activities, problems concentrating,loneliness, self-loathing, apathy or indifference, depersonalization,loss of interest in sexual activity, shyness or social anxiety,irritability, chronic pain, lack of motivation, and morbid/suicidalideation) to mania (e.g., elation, euphoria, irritation, and/orsuspicious). Bipolar disorder is defined and classified in DSM-IV-TR.Bipolar disorder includes bipolar I disorder, bipolar II disorder,cyclothymia, and bipolar disorder not otherwise specified. Bipolardisorder is a common, severe, chronic and one of the most debilitatingof all medical illnesses. Patients afflicted with this disordertypically alternate between episodes of depression (depressed mood,hopelessness, anhedonia, varying sleep disturbances, difficulty inconcentration, psychomotor retardation and often, suicidal ideation) andepisodes of mania (grandiosity, euphoria, racing thoughts, decreasedneed for sleep, increased energy, risk taking behavior).

Treatment of bipolar disorder can be assessed in clinical trials usingrating scales such as the Montgomery-Asberg Depression Rating Scale, theHamilton Depression Scale, the Raskin Depression Scale, Feighnercriteria, and/or Clinical Global Impression Scale Score (Gijsman et al.,Am J Psychiatry 2004, 161, 1537-1547; and Post et al., J Clin Psychiatry2005, 66(3), 370-374).

Depressive disorders include major depressive disorder, dysthymicdisorder, premenstrual dysphoric disorder, minor depressive disorder,recurrent brief depressive disorder, and postpsychotic depressivedisorder of schizophrenia (see DSM IV).

GABA_(B) antagonists are also useful in the treatment of depressivemoods or anxiety states (see e.g., Slattery et al., J. Pharmacol. Exp.Ther. 2005, 312, 290-296; and Nakagawa et al., Eur. J. Pharmacol. 1999,381, 1-7).

The efficacy of compounds provided by the present disclosure fortreating depression can be evaluated in animal models of depression suchas the forced swim test (Porsolt et al., Nature 1977, 266, 525-532; andPorsolt et al., Arch Int Pharmacodyn 1997, 229, 327-336), the tailsuspension test (Cryan et al., Trends Pharmacol Sci 2002, 23, 238-245;and Cryan and Mombereau, Mol Psychiatr 2004, 9, 1050-1062), and well asother (Porsolt, Rev. Neurosci 2000, 11, 53-58).

In certain embodiments, prodrugs of 3-aminopropylphosphinic acid analogsprovided by the present disclosure can be useful in treating anxiety.Anxiety is defined and classified in DSM-IV-TR. Anxiety disordersinclude panic attack, agoraphobia, panic disorder without agoraphobia,agoraphobia without history of panic disorder, specific phobia, socialphobia, obsessive-compulsive disorder, posttraumatic stress disorder,acute stress disorder, generalized anxiety disorder, anxiety disorderdue to a general medical condition, substance-induced anxiety disorder,and anxiety disorder not otherwise specified.

Useful animal models for assessing treatment of anxiety includefear-potentiated startle (Brown et al., J Experimental Psychol 1951, 41,317-327); elevated plus-maze (Pellow et al., J Neurosci. Methods 1985,14, 149-167; and Hogg, Pharmacol Biochem Behavior 1996, 54(1), 21-20);fear-potentiated behavior in the elevated plus-maze test (Korte and DeBoer, Eur J Pharmacol 2003, 463, 163-175); X-maze test of anxiety(Handley and Mithani, Arch Pharmacol 1984, 327, 1-5); and rat socialinteraction test (File, J Neurosci Methods 1980, 2, 219-238). Geneticanimal models of anxiety are known (Toh, Eur J Pharmacol 2003, 463,177-184) as are other animal models sensitive to anti-anxiety agents(Martin, Acta Psychiatr Scand 1998, Suppl 393, 74-80).

In clinical trials, efficacy can be evaluated using psychologicalprocedures for inducing experimental anxiety applied to healthyvolunteers and patients with anxiety disorders (see e.g., Graeff, etal., Brazilian J Medical Biological Res 2003, 36, 421-32) or byselecting patients based on the Structured Clinical interview for DSM-IVAxis I Disorders as described by First et al., Structured ClinicalInterview for DSM-IV Axis I Disorders, Patient Edition (SCIDIP), Version2. Biometrics Research, New York State Psychiatric Institute, New York,1995. One or more scales can be used to evaluate anxiety and theefficacy of treatment including, for example, the Penn State WorryQuestionnaire (Behar et al., J Behav Ther Exp Psychiatry 2003, 34,25-43), the Hamilton Anxiety and Depression Scales, the SpielbergerState-Trait Anxiety Inventory, and the Liebowitz Social Anxiety Scale(Hamilton, J Clin Psychiatry 1980, 41, 21-24; Spielberger and Vagg, JPersonality Assess 1984, 48, 95-97; and Liebowitz, J Clin Psychiatry1993, 51, 31-35 (Suppl)).

In certain embodiments, prodrugs of 3-aminopropylphosphinic acid analogsprovided by the present disclosure can be useful in treating seizuredisorders such as epilepsy. Seizure disorders such as epilepsy involveperiodic disturbances of the brain's electrical activity, resulting insome degree of temporary brain dysfunction. Seizures can be localized(partial or focal onset seizures) or distributed (generalized seizures).Partial seizures can be simple, in which a person is completelyconscious and aware of the surroundings, or complex, in whichconsciousness is impaired but not completely lost. Partial seizuresinclude simple partial seizures, Jacksonian seizures, complex partialseizures, and epilepsia partialis continua. Generalized seizures cause aloss of consciousness and abnormal movements. Generalized seizuresinclude tonic-clonic seizures, primary generalized epilepsy, bsenceseizures, atonic seizures, myoclonic seizures, and status epilepticus.

GABA_(B) antagonists are also useful in the treatment of epilepsy,particularly “petit-mal” type epilepsy, including spontaneous absenceepilepsy and atypical absence epilepsy (see e.g., Marescaux et al., U.S.Pat. No. 5,407,922; Marescaux et al., U.S. Pat. No. 5,545,631; Czuczwarand Patsalos, CNS Drugs, 2001, 15, 339-350; Getova et al., Eur. J.Pharmacol. 1997, 320, 9-13; Vergnes et al., Eur. J. Pharmacol. 1997,332, 245-255; and Marescaux et al., J. Neural Transm. 1992, 35,179-188).

Animal models that are useful for evaluating the efficacy of compoundsfor treating seizure disorders are known (see, e.g., Murashima et al,Epilepsia 2002, 43(Suppl. 5), 130-135; and Kudin et al., Eur J Neurosci2002, 15, 1105-14)).

Doses

3-Aminopropylphosphinic acid analog prodrugs of Formula (I) may beadministered to treat diseases or disorders such as mild cognitiveimpairment, cognitive impairment associated with Alzheimer's disease,depression, anxiety, epilepsy, and others disclosed herein.

The amount of 3-aminopropylphosphinic acid analog prodrugs of Formula(I) that will be effective in the treatment of a particular disorder orcondition disclosed herein will depend on the nature of the disorder orcondition, and may be determined by standard clinical techniques knownin the art. In addition, in vitro or in vivo assays may optionally beemployed to help identify optimal dosage ranges. The amount of acompound administered will, of course, be dependent on, among otherfactors, the subject being treated, the weight of the subject, theseverity of the affliction, the manner of administration, and thejudgment of the prescribing physician.

In certain embodiments, the dosage forms are adapted to be administeredto a patient no more than twice per day, and in certain embodiments,only once per day. Dosing may be provided alone or in combination withother drugs and may continue as long as required for effective treatmentof the disease state or disorder.

Suitable dosage ranges for oral administration are dependent on thepotency of the parent 3-aminopropylphosphinic acid analog. For certain3-aminopropylphosphinic acid analogs, doses are generally between about0.1 mg to about 20 mg per kilogram body weight. Other3-aminopropylphosphinic acid analogs may be more potent and lower dosesmay be appropriate for both the parent drug and any prodrug (measured onan equivalent molar basis). Dosage ranges may be readily determined bymethods known to the skilled artisan.

Combination Therapy

In certain embodiments, 3-aminopropylphosphinic acid analog prodrugs ofFormula (I) or pharmaceutically acceptable salts or solvates thereof asdisclosed herein, may be used in combination therapy with at least oneother therapeutic agent. 3-Aminopropylphosphinic acid analog prodrugs ofFormula (I) and the other therapeutic agent(s) may act additively or,and in certain embodiments, synergistically. In certain embodiments, a3-aminopropylphosphinic acid analog prodrug of Formula (I) may beadministered concurrently with the administration of another therapeuticagent, such as for example, an anti-depressant, anxiolytic, sedative,non-steroidal anti-inflammatory drug, selective serotonin reuptakeinhibitor, monoamine oxidase inhibitor, psychostimulant, antipsychotic,anticonvulsant, or sedative. In certain embodiments, a3-aminopropylphosphinic acid analog prodrug of Formula (I) orpharmaceutically acceptable salts or solvates thereof may beadministered prior or subsequent to administration of anothertherapeutic agent, such as for example, an antidepressant, anxiolytic,sedative, non-steroidal anti-inflammatory drug, selective serotoninreuptake inhibitor, monoamine oxidase inhibitor, psychostimulant,antipsychotic, or anticonvulsant.

Pharmaceutical compositions of the present disclosure may include, inaddition to one or more compounds of the present disclosure, one or moretherapeutic agents effective for treating the same or different disease,disorder, or condition.

Methods of the present disclosure include administration of one or morecompounds or pharmaceutical compositions of the present disclosure andone or more other therapeutic agents provided that the combinedadministration does not inhibit the therapeutic efficacy of the one ormore compounds of the present disclosure and/or does not produce adversecombination effects.

In certain embodiments, compositions of the present disclosure may beadministered concurrently with the administration of another therapeuticagent, which may be part of the same pharmaceutical composition as, orin a different composition from, that containing the compounds of thepresent disclosure. In certain embodiments, compounds of the presentdisclosure may be administered prior or subsequent to administration ofanother therapeutic agent. In certain embodiments of combinationtherapy, the combination therapy comprises alternating betweenadministering a composition of the present disclosure and a compositioncomprising another therapeutic agent, e.g., to minimize adverse sideeffects associated with a particular drug. When a compound of thepresent disclosure is administered concurrently with another therapeuticagent that potentially may produce adverse side effects including, butnot limited to, toxicity, the therapeutic agent may advantageously beadministered at a dose that falls below the threshold at which theadverse side effect is elicited.

In certain embodiments, a drug may further comprise substances toenhance, modulate and/or control release, bioavailability, therapeuticefficacy, therapeutic potency, stability, and the like. For example, toenhance therapeutic efficacy a drug may be co-administered with one ormore active agents to increase the absorption or diffusion of the drugfrom the gastrointestinal tract, or to inhibit degradation of the drugin the systemic circulation. In certain embodiments, a drug may beco-administered with active agents having pharmacological effects thatenhance the therapeutic efficacy of the drug.

In certain embodiments, compounds or pharmaceutical compositions of thepresent disclosure include, or may be administered to a patient togetherwith, another compound for treating anxiety, drugs for treating seizuredisorders such as epilepsy, drugs for treating cognitive or memorydisorders, or drugs for treating depression.

Examples of drugs for treating mood disorders such as anxiety includebenzodiazepines such as alprazolam, chlordiazepoxide, clonazepam,clorazepate, diazepam, lorazepam, and oxazepam; antidepressantsincluding tricyclic antidepressants such as amitriptyline, amoxapine,clomipramine, desipramine, doxepin, imipramine, maprotiline,nortriptyline, protriptyline, and trimipramine, selective serotoninreuptake inhibitors such as citalopram, fluoxetine, fluvoxamine,paroxetine, and sertraline; monoamine oxidase inhibitors such asphenelzine and tranylcypromine, and other antidepressants such asbupropion, mirtazapine, nefazodone, trazodone, and venlafaxine; andother anxiolytics such as hydroxyzine, mecloqualone, medetomidine,metomidate, adinazolam, chlordiazepoxide, clobenzepam, flurazepam,lorazepam, loprazolam, midazolam, alpidem, alseroxlon, amphenidone,azacyclonol, bromisovalum, captodiamine, capuride, carbcloral,carbromal, chloralbetaine, enciprazine, flesinoxan, ipsapiraone,lesopitron, loxapine, methaqualone, methprylon, propanolol,tandospirone, trazadone, zopiclone, and zolpidem.

Examples of drugs for treating mood disorders such as depression includetricyclic antidepressants such as amitriptyline, amoxapine,clomipramine, desipramine, doxepin, imipramine, maprotiline,nortriptyline, protriptyline, and trimipramine; selective serotoninreuptake inhibitors such as citalopram, escitalopram, fluoxetine,fluvoxamine, paroxetine, and sertraline; serotonin-noradrenalinereuptake inhibitors such as venlafaxine, duloxetine, sibutramine, andmilnacipran; monoamine oxidase inhibitors such as phenelzine andtranylcypromine; and psychostimulants such as dextroamphetamine andmethylphenidate. Other antidepressants include benmoxine, butriptyline,dosulepin, imipramine, kitanserin, lofepramine, medifoxamine, mianserin,mirtazapine, viloxazine, cotinine, nisoxetine, reboxetine, tianeptine,acetaphenazine, binedaline, brofaromine, cericlamine, clovoxamine,iproniazid, isocarboxazid, moclobemide, phenyhydrazine, selegiline,sibutramine, ademetionine, adrafinil, amesergide, amisulpride,amperozide, benactyzine, bupropion, caroxazone, gepirone, idazoxan,metralindole, minaprine, nefazodone, nomifensine, ritanserin, roxindole,S-adenosylmethionine, escitalopram, tofenacin, trazodone, tryptophan,zalospirone, and Saint John's wort. Compounds and compositions of thepresent disclosure may also be used in conjunction with psychotherapy orelectroconvulsive therapy to treat mood disorders such as depression.

Examples of drugs for treating seizures such as epilepsy includeanticonvulsants such as carbamazepine, clonazepam, divalproex,ethosuximide, felbamate, fosphenyloin, gabapentin, lamotrigine,levetiracetam, lorazepam, midazolam, oxcarbazepine, phenobarbital,phenyloin, primidone, tiagabine, topiramate, valproic acid, vigabatrin,and zonisamide; and sedatives such as diazepam and lorazepam.

Examples of drugs for treating cognitive or memory disorders includeantipsychotic drugs such as chlorpromazine, fluphenazine, haloperidol,loxapine, mesoridazine, molindone, perphenazine, pimozide, thioridazine,thiothixene, trifluoperazine, aripiprazole, clozapine, olanzapine,quetiapine, risperidone, and ziprasidone; sedatives such as diazepam andlorazepam; benzodiazepines such as alprazolam, chlordiazepoxide,clonazepam, clorazepate, diazepam, lorazepam, and oxazepam; nonsteroidalanti-inflammatory drugs such as aceclofenac, acetaminophen,alminoprofen, amfenac, aminopropylon, amixetrine, aspirin, benoxaprofen,bromfenac, bufexamac, carprofen, celecoxib, choline, salicylate,cinchophen, cinmetacin, clopriac, clometacin, diclofenac, diflunisal,etodolac, fenoprofen, flurbiprofen, ibuprofen, indomethacin, indoprofen,ketoprofen, ketorolac, mazipredone, meclofenamate, nabumetone, naproxen,parecoxib, piroxicam, pirprofen, rofecoxib, sulindac, tolfenamate,tolmetin, and valdecoxib; acetylcholinesterase inhibitors such asdonepezil, galantamine, rivastigmine, physostigmine, and tacrine; orN-methyl-D-aspartate (NMDA) receptor blockers such as memantine.

EXAMPLES

The following examples describe in detail preparation of compoundsdisclosed herein. It will be apparent to those of ordinary skill in theart that many modifications, both to materials and methods, may bepracticed.

In the examples below, the following abbreviations have the followingmeanings. If an abbreviation is not defined, it has its generallyaccepted meaning.

Atm=atmosphere

Boc=tert-butyloxycarbonyl

Cbz=carbobenzyloxy

DCC=dicyclohexylcarbodiimide

DMAP=4-N,N-dimethylaminopyridine

DMF=N,N-dimethylformamide

DMSO=dimethylsulfoxide

g=gram

h=hour

HPLC=high pressure liquid chromatography

L=liter

LC/MS=liquid chromatography/mass spectroscopy

M=molar

min=minute

mL=milliliter

mmol=millimoles

NHS=N-hydroxysuccinimide

THF=tetrahydrofuran

TFA=trifluoroacetic acid

TLC=thin layer chromatography

TMS=trimethylsilyl

μL=microliter

μM=micromolar

v/v=volume to volume

Synthesis of Chemical Intermediates Useful in Synthesizing AcyloxyalkylCarbamate Prodrugs of 3-Aminopropylphosphinic Acid

O-(1-Isobutanoyloxyethyl) S-methyl thiocarbonate (2) was synthesizedusing a two-step process. In a first step (Step A), a 21% (w/w) aqueoussolution of sodium methylthiolate (580.7 g, 1.74 mol) was added to asolution of 1-chloroethyl chloroformate (250 g, 1.74 mol) andtetrabutylammonium hydrogensulfate (5.9 g, 17 mmol) in CH₂Cl₂ (450 mL)over 2 h. The reaction mixture was stirred for an additional hour, thenworked-up by separating the aqueous phase and extracting the organicphase with brine (2×250 mL). The organic phase was dried over anhydroussodium sulfate and concentrated in vacuo. The residue was purified byvacuum distillation to afford O-(1-chloroethyl) S-methyl thiocarbonate(3) as a colorless liquid (277.3 g, 97% yield). ¹H NMR (CDCl₃, 400 MHz):δ 1.82 (d, J=5.6 Hz, 3H), 2.38 (s, 3H), 6.57 (q, J=5.2 Hz, 1H).

In a second step (Step B), compound (3) (308 g, 2 mol) was dissolved inisobutyric acid (264 g, 3 mol). This mixture was slowly added to apre-mixed solution of isobutyric acid (264 g, 3 mol) anddiisopropylethylamine (387 g, 3 mol), and the reaction mixture heated to55° C. for 16 h, diluted with ether (10 L), washed with water (4×5 L),saturated bicarbonate solution (2×5 L) and brine (5 L), then dried overanhydrous sodium sulfate, filtered, and concentrated in vacuo to givecompound (2) as a colorless liquid (400 g, 97% yield). The product wasoptionally further purified by vacuum distillation (135° C./20 Torr). ¹HNMR (CDCl₃, 400 MHz): δ1.17 (d, J=6.8 Hz, 6H), 1.49 (d, J=5.6 Hz, 3H),2.33 (s, 3H), 2.54 (m, 1H), 6.91 (q, J=5.2 Hz, 1H).

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing isobutyric acid with n-butyricacid in Step B affords O-(1-butanoyloxyethyl) S-methyl thiocarbonate (4)as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing isobutyric acid with pivalicacid in Step B affords O-(1-pivaloyloxyethyl) S-methyl thiocarbonate (5)as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing isobutyric acid withcyclohexanecarboxylic acid in Step B affords O-(cyclohexylethyl)S-methyl thiocarbonate (6) as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing isobutyric acid with benzoicacid in Step B affords O-(benzoyloxyethyl) S-methyl thiocarbonate (215)as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing 1-chloroethyl chloroformatewith chloromethyl chloroformate in Step A affordsO-(isobutanoyloxymethyl) S-methyl thiocarbonate (7) as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing 1-chloroethyl chloroformatewith chloromethyl chloroformate in Step A and replacing isobutyric acidwith n-butyric acid in Step B affords O-(butanoyloxymethyl) S-methylthiocarbonate (8) as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing 1-chloroethyl chloroformatewith chloromethyl chloroformate in Step A and replacing isobutyric acidwith pivalic acid in Step B affords O-(pivaloyloxymethyl) S-methylthiocarbonate (9) as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing 1-chloroethyl chloroformatewith chloromethyl chloroformate in Step A and replacing isobutyric acidwith cyclohexanecarboxylic acid in Step B affordsO-(cyclohexanoyloxymethyl) S-methyl thiocarbonate (10) as an oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyethyl)S-methyl thiocarbonate (2) and replacing 1-chloroethyl chloroformatewith chloromethyl chloroformate in Step A and replacing isobutyric acidwith benzoic acid in Step B affords O-(benzoyloxymethyl) S-methylthiocarbonate (213) as an oil.

O-(1-Isobutanoyloxyisobutoxy) S-methyl thiocarbonate (11) wassynthesized in a three-step process. In a first step (Step A), asolution of 1-chloro-2-methylpropyl chloroformate (1026 g, 6.0 mol) andtetrabutylammonium hydrogensulfate (20 g, 60 mmol) in dichloromethane(1500 mL) in a jacketed 10 L reactor equipped with a mechanical stirrer,temperature probe, and addition funnel was cooled to 10° C. To thereaction mixture was gradually added a 15% aqueous solution of sodiummethylthiolate (3 L, 6.4 mol) over 4 h. The reaction was moderatelyexothermic and the internal temperature was maintained between 10 and20° C. during the addition. The aqueous phase was separated and theorganic phase was washed with brine (2×2 L) and water (2 L). The organiclayer was dried over anhydrous Na₂SO₄, filtered, and concentrated underreduced pressure to afford O-(1-chloroisobutoxy) S-methyl thiocarbonate(12) (1050 g, 5.76 mol, 96% yield) as a colorless liquid. ¹H NMR (CDCl₃,400 MHz): δ 1.1 (dd, 6H), 2.2 (m, 1H), 2.4 (s, 3H), 6.35 (d, 1H).

In a second step (Step B), to a 20 L round bottom flask was addedisobutyric acid (1300 mL, 14 mol), and an aqueous solution of 25%tetramethylammonium hydroxide (5 L, 14 mol). The water was removed underreduced pressure, and azeotroped with toluene (2×2 L) to leavetetramethylammonium isobutyrate (13) as an amber liquid, which was usedwithout further purification.

In a third step (Step C), to a 3 L three neck round bottom flaskequipped with a mechanical stirrer and Teflon-coated thermocouple wasadded compound (13) (1672 g, 9 mol), isobutyric acid (264 g, 1.5 mol),and compound (12) (1050 g, 5.76 mol). The reaction mixture was heated to80° C. for 12 h, monitoring the reaction progress by ¹H NMR. Thereaction mixture was cooled to 20° C., diluted with EtOAc (1 L) andwashed with water (2×1 L), saturated NaHCO₃ (1×2 L) and water (1 L). Theorganic phase was separated and concentrated under reduced pressure toafford O-(1-isobutanoyloxyisobutoxy) S-methyl thiocarbonate (11) (905 g,3.9 mol, 65%) as a colorless liquid. ¹H NMR (CDCl₃, 400 MHz): δ 1.0 (d,6H), 1.2 (dd, 6H), 2.05 (m, 1H), 2.35 (s, 3H), 2.6 (m, 1H), 6.7 (d, 1H).

Following the procedures for synthesizing O-(1-isobutanoyloxyisobutoxy)S-methyl thiocarbonate (11) and replacing isobutyric acid with n-butyricacid affords O-(1-butanoyloxyisobutoxy) S-methyl thiocarbonate (14) asan oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyisobutoxy)S-methyl thiocarbonate (11) and replacing isobutyric acid with pivalicacid affords O-(1-pivaloyloxyisobutoxy) S-methyl thiocarbonate (15) asan oil.

Following the procedures for synthesizing O-(1-isobutanoyloxyisobutoxy)S-methyl thiocarbonate (11) and replacing isobutyric acid withcyclohexanecarboxylic acid affords O-(1-cyclohexanoyloxyisobutoxy)S-methyl thiocarbonate (16) as an oil.

[(1-Isobutanoyloxyethoxy)carbonyloxy]succinimide (17) was synthesizedusing the following procedure. To a solution of compound (2) (1 g, 4.8mmol) in CH₂Cl₂ (10 mL) was added N-hydroxysuccinimide (1.1 g, 9.5 mmol)and the reaction mixture cooled to 0° C. A solution of 32% (v/v)peracetic acid in acetic acid (3.4 mL, 1.1 g, 14.4 mmol) was addeddropwise over a period of 10 min, then the solution allowed to stir atroom temperature for 3 h. The reaction mixture was diluted with ether(50 mL) and washed with water (2×10 mL), saturated sodium bicarbonatesolution (10 mL) and brine (10 mL), then dried over anhydrous sodiumsulfate, filtered, and concentrated in vacuo to give compound (17) as aas colorless oil (1 g, 77% yield). After trituration with hexane (20 mL)the product solidified to a white solid. m.p: 50-54° C. ¹H NMR (CDCl₃,400 MHz): δ1.17 (d, J=6.8 Hz, 6H), 1.56 (d, J=5.6 Hz, 3H), 2.55 (m, 1H),2.82 (s, 4H), 6.80 (q, J=5.2 Hz, 1H). MS (ESI) m/z 296.4 (M+Na)⁺.

Following the procedures for synthesizing[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (4) affords[(1-butanoyloxyethoxy)carbonyloxy]succinimide (18).

Following the procedures for synthesizing[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (5) affords[(1-pivaloyloxyethoxy)carbonyloxy]succinimide (19).

Following the procedures for synthesizing[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (6) affords[(1-cyclohexanoyloxyethoxy)carbonyloxy]succinimide (20).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (215) affords[(1-benzoyloxyethoxy)carbonyloxy]succinimide (216).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (7) affords[(isobutanoyloxymethoxy)carbonyloxy]succinimide (21).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (8) affords[(butanoyloxymethoxy)carbonyloxy]succinimide (22).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (9) affords[(pivaloyloxymethoxy)carbonyloxy]succinimide (23).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (10) affords[(cyclohexanoyloxymethoxy)carbonyloxy]succinimide (24).

Following the procedures for synthesizing

[(1-isobutanoyloxyethoxy)carbonyloxy]succinimide (17) and replacingcompound (2) with compound (213) affords[(benzoyloxymethoxy)carbonyloxy]succinimide (214).

(1R)-1-[((3S,4S)-2,5-Dioxo-3,4-dibenzoyloxypyrrolidinyl)-oxycarbonyloxy]-2-methylpropyl2-methylpropanoate (25) was synthesized in a three-step process. In afirst step (Step A), a suspension of 2,3-dibenzoyl-D-tartaric acid (100g, 279 mmol) in acetic anhydride (300 mL) was stirred at 85° C. for 2 hthen the reaction mixture allowed to cool to room temperature. Thecrystalline product was collected by filtration, washed with a mixtureof ether and hexane (1:1) and dried under vacuum to afford(3S,4S)-2,5-dioxo-3,4-dibenzoyloxy-3,4-dihydrofuran (26) (80 g, 84%yield). ¹H NMR (CDCl₃, 400 MHz): δ 5.99 (s, 2H), 7.50 (m, 4H), 7.66 (m,2H), 8.07 (m, 4H).

In a second step (Step B), to a suspension of (26) (60 g, 176 mmol) in amixture of acetonitrile and water (8:1, 400 mL) at 0° C. was added a 50%aqueous solution of hydroxylamine (13.0 mL, 211 mmol). The resultingsuspension was stirred overnight at room temperature to obtain a clearsolution. The bulk of the acetonitrile was removed by rotary evaporationand the residue was portioned between ethyl acetate and water. Theorganic phase was washed successively with water and brine, dried overanhydrous Na₂SO₄ and concentrated in vacuo to afford the intermediate,2,3-dibenzoyloxy D-tartaric acid mono-hydroxamate. This compound wassuspended in toluene heated under reflux for 2 h, then cooled to roomtemperature to form a crystalline solid. The product was collected byfiltration, washed with a mixture of ether and hexane (1:1), and driedunder vacuum to afford1-hydroxy-(3S,4S)-2,5-dioxo-3,4-dibenzoyloxypyrrolidine (27) (58 g,93%). ¹H NMR (CDCl₃, 400 MHz): δ 6.06 (s, 2H), 7.50 (t, 4H), 7.65 (dt,2H), 8.06 (m, 4H). MS (ESI) m/z 354.00 (M−H)⁻.

In a third step (Step C), to a stirred solution of compound (27) (35 g,98.6 mmol) and thiocarbonate (11) (34.6 g, 148 mmol) in dichloromethaneat 0° C. was dropwise added a 32% solution of peracetic acid (300 mmol)in acetic acid over 2 h. The reaction temperature was kept below 35° C.during the addition of peracetic acid. After the addition was complete,the reaction mixture was stirred overnight at room temperature. Theresulting white precipitate was filtered and washed successively withwater, and a mixture of ether and hexane (1:2), then dried under vacuumto afford the crude title compound. This product was crystallized oncefrom a mixture of ethyl acetate and hexane (1:1) to afford(1R)-1-[((3S,4S)-2,5-dioxo-3,4-dibenzoyloxypyrrolidinyl)-oxycarbonyloxy]-2-methylpropyl2-methylpropanoate (25) (13.7 g, 25% yield). The diastereomeric purityof the product was determined to be 98.4% d.e. by HPLC using a chiralcolumn. ¹H NMR (CDCl₃, 400 MHz): δ 1.06 (d, 6H), 1.22 (d, 3H), 1.22 (d,3H), 2.20 (m, 1H), 2.64 (hept. 1H), 6.01 (br. s, 2H), 6.64 (d, 1H), 7.47(m, 4H), 7.63 (m, 2H), 8.07 (m, 4H).

(1S)-1-[((3R,4R)-2,5-Dioxo-3,4-dibenzoyloxypyrrolidinyl)-oxycarbonyloxy]-2-methylpropyl2-methylpropanoate (28) was synthesized using a three-step process. In afirst step (Step A), to a 3-necked 5 L round bottom flask fitted with amechanical stirrer and a Teflon coated thermocouple was added(−)-2,3-dibenzoyl-L-tartaric acid (1000 g, 2.79 mol) followed by aceticanhydride (2 L). The suspension was stirred and heated to 85° C. for 2 hduring which time the starting material gradually dissolved. A shorttime thereafter, the product began to crystallize in the reactionmixture and the suspension was then cooled to 25° C. The product wascollected by filtration, washed with 10% acetone in hexane (2×1 L), anddried in a vacuum oven at 50° C. overnight to afford(3R,4R)-2,5-dioxo-3,4-dibenzoyloxy-3,4-dihydrofuran (29) as a whitesolid. ¹H NMR (CDCl₃, 400 MHz): δ 6.0 (s, 2H), 7.45 (app. t, 4H), 7.65(app. t, 2H), 8.05 (d, 4H).

In a second step (Step B), to a 3-neck 5 L round bottom flask fittedwith a mechanical stirrer and a Teflon-coated temperature probe wasadded compound (29) (2.79 mol) followed by acetonitrile (2 L). Thesuspension was cooled in an ice bath to 4° C., followed by the additionof 50% aqueous hydroxylamine (180 mL, 2.93 mol) over 1 h. The startingmaterial gradually dissolved during the addition and the reactionmixture was warmed to 20° C. and stirred for 1 h. The reaction mixturewas concentrated in vacuo, diluted with EtOAc (1 L) and washed with 1 NHCl (2×1 L). The organic phase was separated and concentrated in vacuoto afford a viscous, red syrup. The syrup was then heated for two hoursin toluene (2.5 L) at 100° C. with azeotropic removal of water. Thesyrup gradually dissolved and then the product crystallized. Aftercooling to room temperature the solid was collected by filtration,washed with 10% acetone in hexane (2×1 L) and dried in a vacuum oven toafford 1-hydroxy-(3R,4R)-2,5-dioxo-3,4-dibenzoyloxypyrrolidine (30) (862g, 2.43 mol, 87% yield) as a white solid. ¹H NMR (CDCl₃, 400 MHz): δ5.85 (s, 2H), 7.45 (app. t, 4H), 7.65 (app t, 2H), 8.05 (m, 4H).

In a third step (Step C), a 3 L three necked round bottom flask fittedwith a mechanical stirrer, Teflon coated temperature probe and anaddition funnel was charged with compound (11) (234 g, 1 mol), compound(30) (330 g, 0.95 mol), and 1,2-dichloroethane (2200 mL). The reactionmixture was cooled under a nitrogen atmosphere in an ice water bath to15° C. To the stirred reaction mixture was added a 39% solution ofperacetic acid in dilute acetic acid (500 mL, 2.94 mol) over 2 h,maintaining the temperature between 15 and 22° C. This temperature wasmaintained for an additional 12 h during which time a white precipitatewas formed. The reaction mixture was further cooled to 3-4° C., theproduct collected by filtration, and washed with hexane (2×1 L). Theproduct was dried in vacuo, yielding(1S)-1-[((3R,4R)-2,5-dioxo-3,4-dibenzoyloxypyrrolidinyl)-oxycarbonyloxy]-2-methylpropyl2-methylpropanoate (28) (128 g, 0.24 mol, 25% yield). The diastereomericpurity of the product was determined to be >99% d.e. by HPLC using achiral column. ¹H NMR (CDCl₃, 400 MHz): δ 1.0 (d, 6H), 1.2 (dd, 6H), 2.1(m, 1H), 2.65 (m, 1H), 6.0 (br. s, 2H), 6.6 (d, 1H), 7.45 (app. t, 4H),7.65 (app. t, 2H), 8.05 (d, 4H).

Example 1 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(31)

To a solution of 3-aminopropyl(n-butyl)phosphinic acid (10 mmol) andsodium bicarbonate (20 mmol) in water (40 mL) was added a solution ofcompound (17) (10 mmol) in acetonitrile (20 mL) over 1 min. The reactionwas stirred at ambient temperature for 16 h. The reaction mixture wasdiluted with ethylacetate (100 mL) and washed with 0.1 M aqueouspotassium bisulfate (3×100 μL). The organic phase was separated, driedover anhydrous magnesium sulfate, filtered, and concentrated in vacuo toafford the title compound (31) as a white solid. ¹H-NMR (400 MHz,CDCl₃): δ 6.78 (q, J=8 Hz, 1H), 3.49 (s, 1H), 3.28 (t, J=6.4 Hz, 2H),2.51-2.55 (m, 1H), 1.80-1.84 (m, 2H), 1.65-1.75 (m, 3H), 1.55-1.58 (m,2H), 1.39-1.48 (m, 4H), 1.17 (d, J=8.4 Hz, 9H), 0.93 (t, J=7.2 Hz, 3H).Phosphorus (162 MHz, CDCl₃) δ0.31. MS (ESI) m/z 338 (M+H)⁺.

Example 2 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(32)

Following the procedure of Example 1 and replacing compound (17) withcompound (18) affords the title compound (32) as a white solid.

Example 3 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(33)

Following the procedure of Example 1 and replacing compound (17) withcompound (19) affords the title compound (33) as a white solid.

Example 4 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinicAcid (34)

Following the procedure of Example 1 and replacing compound (17) withcompound (20) afforded the title compound (34) as a white solid. ¹H-NMR(400 MHz, CDCl₃): δ 7.42 (br, 1H), 6.76 (q, J=5.6 Hz, 1H), 3.25 (br,2H), 2.24-2.30 (m, 1H), 1.19-1.90 (m, 20H). MS (ESI) m/z 336 (M+H)⁺

Example 5 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(35)

Following the procedure of Example 1 and replacing compound (17) withcompound (21) afforded the title compound (35) as a white solid. ¹H-NMR(400 MHz, CDCl₃): δ 5.71 (s, 2H), 3.29-3.32 (t, J=6.8 Hz, 2H), 2.57-2.61(m, 1H), 1.73-1.84 (m, 2H), 1.68-1.72 (m, 4H), 1.55-1.57 (m, 2H),1.38-1.44 (m, 2H), 1.18 (d, J=7.2 Hz), 0.9 (t, J=7.2 Hz, 3H). Phosphorus(162 MHz, CD₃OD) δ0.61

MS (ESI) m/z 324 (M+H)⁺.

Example 6 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid (36)

Following the procedure of Example 1 and replacing compound (17) withcompound (22) affords the title compound (36) as a white solid.

Example 7 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid (37)

Following the procedure of Example 1 and replacing compound (17) withcompound (23) affords the title compound (37) as a white solid.

Example 8 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(38)

Following the procedure of Example 1 and replacing compound (17) withcompound (24) affords the title compound (38) as a white solid.

Example 9 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinicAcid (39)

To a 3 L three necked round bottom flask fitted with a mechanicalstirrer, temperature probe, and nitrogen inlet was added compound (25)(100 mmol), 3-aminopropyl(n-butyl)phosphinic acid (100 mmol), THF (1 L),and water (100 mL). The suspension was stirred under a nitrogenatmosphere at 18-20° C. for 4 h during which time the reaction mixturebecame homogeneous. The THF was removed in vacuo and the reactionmixture was diluted with methyl tert-butyl ether (250 mL) and washedwith 1N HCl (1×500 mL) and water (2×200 mL). The organic phase wasseparated and concentrated in vacuo to leave a white solid. The solidwas purified by flash chromatography to afford the product (39) as awhite solid. ¹H-NMR (400 MHz, CD₃OD): δ 6.74-6.70 (q, J=5.2, 1H),4.06-3.96 (m, 1H), 3.22-3.21 (m, 2H), 2.547-2.477 (m, 1H), 1.92-1.84 (m,2H), 1.52-1.48 (s, 3H), 1.142-1.138 (d, J=1.6, 3.0H), 1.124-1.121 (dd,J=1.6, 3.0H). Phosphorus (162 MHz, CD₃OD): δ1.04; MS (ESI) m/z 346(M+H)⁺)

Example 10 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinicAcid (40)

Following the procedure of Example 9 and replacing compound (25) withcompound (28) affords the title compound (40) as a white solid.

Example 11 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (41)

Following the procedure of Example 1 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (41) as a white solid.

Example 12 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (42)

Following the procedure of Example 2 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (42) as a white solid.

Example 13 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (43)

Following the procedure of Example 3 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (43) as a white solid.

Example 14 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (44)

Following the procedure of Example 4 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (44) as a white solid.

Example 15 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (45)

Following the procedure of Example 5 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (45) as a white solid.

Example 16 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (46)

Following the procedure of Example 6 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (46) as a white solid.

Example 17 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (47)

Following the procedure of Example 7 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (47) as a white solid.

Example 18 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (48)

Following the procedure of Example 8 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (48) as a white solid.

Example 19 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (49)

Following the procedure of Example 9 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (49) as a white solid.

Example 20 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-hydroxypropyl(n-butyl)phosphinicAcid (50)

Following the procedure of Example 10 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (50) as a white solid.

Example 21 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (51)

Following the procedure of Example 1 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (51) as a white solid.

Example 22 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (52)

Following the procedure of Example 2 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (52) as a white solid.

Example 23 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (53)

Following the procedure of Example 3 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (53) as a white solid.

Example 24 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (54)

Following the procedure of Example 4 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (54) as a white solid.

Example 25 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (55)

Following the procedure of Example 5 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (55) as a white solid.

Example 26 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (56)

Following the procedure of Example 6 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (56) as a white solid.

Example 27 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (57)

Following the procedure of Example 7 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (57) as a white solid.

Example 28 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (58)

Following the procedure of Example 8 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (58) as a white solid.

Example 29 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (59)

Following the procedure of Example 9 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (59) as a white solid.

Example 30 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-hydroxypropyl(n-butyl)phosphinicAcid (60)

Following the procedure of Example 10 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(n-butyl)phosphinic acid affords the titlecompound (60) as a white solid.

Example 31 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (61)

Following the procedure of Example 1 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (61) as a white solid.

Example 32 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (62)

Following the procedure of Example 2 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (62) as a white solid.

Example 33 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (63)

Following the procedure of Example 3 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (63) as a white solid.

Example 34 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (64)

Following the procedure of Example 4 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (64) as a white solid.

Example 35 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (65)

Following the procedure of Example 5 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (65) as a white solid.

Example 36 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (66)

Following the procedure of Example 6 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (66) as a white solid.

Example 37 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (67)

Following the procedure of Example 7 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (67) as a white solid.

Example 38 Synthesis of 3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinic Acid (68)

Following the procedure of Example 8 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (68) as a white solid.

Example 39 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (69)

Following the procedure of Example 9 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (69) as a white solid.

Example 40 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-fluoropropyl(n-butyl)phosphinicAcid (70)

Following the procedure of Example 10 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2R)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (70) as a white solid.

Example 41 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (71)

Following the procedure of Example 1 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (71) as a white solid.

Example 42 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (72)

Following the procedure of Example 2 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (72) as a white solid.

Example 43 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (73)

Following the procedure of Example 3 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (73) as a white solid.

Example 44 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (74)

Following the procedure of Example 4 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (74) as a white solid.

Example 45 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (75)

Following the procedure of Example 5 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (75) as a white solid.

Example 46 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (76)

Following the procedure of Example 6 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (76) as a white solid.

Example 47 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (77)

Following the procedure of Example 7 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (77) as a white solid.

Example 48 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (78)

Following the procedure of Example 8 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (78) as a white solid.

Example 49 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (79)

Following the procedure of Example 9 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (79) as a white solid.

Example 50 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-fluoropropyl(n-butyl)phosphinicAcid (80)

Following the procedure of Example 10 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-(2S)-fluoropropyl(n-butyl)phosphinic acid affords the titlecompound (80) as a white solid.

Example 51 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (81)

Following the procedure of Example 1 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(81) as a white solid.

Example 52 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (82)

Following the procedure of Example 2 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(82) as a white solid.

Example 53 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (83)

Following the procedure of Example 3 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(83) as a white solid.

Example 54 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (84)

Following the procedure of Example 4 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(84) as a white solid.

Example 55 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (85)

Following the procedure of Example 5 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(85) as a white solid.

Example 56 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (86)

Following the procedure of Example 6 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(86) as a white solid.

Example 57 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (87)

Following the procedure of Example 7 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(87) as a white solid.

Example 58 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (88)

Following the procedure of Example 8 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(88) as a white solid.

Example 59 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (89)

Following the procedure of Example 9 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(89) as a white solid.

Example 60 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-2-oxopropyl(n-butyl)phosphinicAcid (90)

Following the procedure of Example 10 and replacing3-aminopropyl(n-butyl)phosphinic acid with3-amino-2-oxopropyl(n-butyl)phosphinic acid affords the title compound(90) as a white solid.

Example 61 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (91)

To a solution of 3-aminopropyl(cyclohexylmethyl)phosphinic acid (10mmol) and sodium bicarbonate (20 mmol) in water (40 mL) is added asolution of compound (17) (10 mmol) in acetonitrile (20 mL) over 1 min.The reaction is stirred at ambient temperature for 16 h. The reactionmixture is diluted with diethyl ether (100 mL) and washed with 0.1 Maqueous potassium bisulfate (3×100 mL). The organic phase is separated,dried over anhydrous magnesium sulfate, filtered, and concentrated invacuo to afford the title compound (91) as a white solid.

Example 62 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (92)

Following the procedure of Example 61 and replacing compound (17) withcompound (18) affords the title compound (92) as a white solid.

Example 63 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (93)

Following the procedure of Example 61 and replacing compound (17) withcompound (19) affords the title compound (93) as a white solid.

Example 64 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (94)

Following the procedure of Example 61 and replacing compound (17) withcompound (20) affords the title compound (94) as a white solid.

Example 65 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (95)

Following the procedure of Example 61 and replacing compound (17) withcompound (21) affords the title compound (95) as a white solid.

Example 66 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (96)

Following the procedure of Example 61 and replacing compound (17) withcompound (22) affords the title compound (96) as a white solid.

Example 67 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (97)

Following the procedure of Example 61 and replacing compound (17) withcompound (23) affords the title compound (97) as a white solid.

Example 68 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (98)

Following the procedure of Example 61 and replacing compound (17) withcompound (24) affords the title compound (98) as a white solid.

Example 69 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (99)

To a 3 L three necked round bottom flask fitted with a mechanicalstirrer, temperature probe, and nitrogen inlet is added compound (25)(100 mmol), 3-aminopropyl(cyclohexylmethyl)phosphinic acid (100 mmol),THF (1 L), and water (100 mL). The suspension is stirred under anitrogen atmosphere at 18-20° C. for 4 h during which time the reactionmixture becomes homogeneous. The THF is removed in vacuo and thereaction mixture is diluted with methyl tert-butyl ether (250 mL) andwashed with 1N HCl (1×500 mL) and water (2×200 mL). The organic phase isseparated and concentrated in vacuo to leave a white solid. The solid ispurified by flash chromatography to afford the product (99) as a whitesolid.

Example 70 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}propyl(cyclohexylmethyl)phosphinicAcid (100)

Following the procedure of Example 69 and replacing compound (25) withcompound (28) affords the title compound (100) as a white solid.

Example 71 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (101)

Following the procedure of Example 61 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (101) as a white solid.

Example 72 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (102)

Following the procedure of Example 62 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (102) as a white solid.

Example 73 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (103)

Following the procedure of Example 63 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (103) as a white solid.

Example 74 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (104)

Following the procedure of Example 64 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (104) as a white solid.

Example 75 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (105)

Following the procedure of Example 65 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (105) as a white solid.

Example 76 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (106)

Following the procedure of Example 66 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (106) as a white solid.

Example 77 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (107)

Following the procedure of Example 67 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (107) as a white solid.

Example 78 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (108)

Following the procedure of Example 68 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (108) as a white solid.

Example 79 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (109)

Following the procedure of Example 69 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (109) as a white solid.

Example 80 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (110)

Following the procedure of Example 70 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (110) as a white solid.

Example 81 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (111)

Following the procedure of Example 61 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (111) as a white solid.

Example 82 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (112)

Following the procedure of Example 62 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (112) as a white solid.

Example 83 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (113)

Following the procedure of Example 63 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (113) as a white solid.

Example 84 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (114)

Following the procedure of Example 64 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (114) as a white solid.

Example 85 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (115)

Following the procedure of Example 65 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (115) as a white solid.

Example 86 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (116)

Following the procedure of Example 66 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (116) as a white solid.

Example 87 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (117)

Following the procedure of Example 67 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (117) as a white solid.

Example 88 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (118)

Following the procedure of Example 68 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (118) as a white solid.

Example 89 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (119)

Following the procedure of Example 69 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (119) as a white solid.

Example 90 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (120)

Following the procedure of Example 70 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (120) as a white solid.

Example 91 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (121)

Following the procedure of Example 61 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (121) as a white solid.

Example 92 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (122)

Following the procedure of Example 62 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (122) as a white solid.

Example 93 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (123)

Following the procedure of Example 63 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (123) as a white solid.

Example 94 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (124)

Following the procedure of Example 64 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (124) as a white solid.

Example 95 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (125)

Following the procedure of Example 65 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (125) as a white solid.

Example 96 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (126)

Following the procedure of Example 66 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (126) as a white solid.

Example 97 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (127)

Following the procedure of Example 67 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (127) as a white solid.

Example 98 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (128)

Following the procedure of Example 68 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (128) as a white solid.

Example 99 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (129)

Following the procedure of Example 69 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (129) as a white solid.

Example 100 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2R)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (130)

Following the procedure of Example 70 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2R)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (130) as a white solid.

Example 101 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (131)

Following the procedure of Example 61 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (131) as a white solid.

Example 102 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (132)

Following the procedure of Example 62 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (132) as a white solid.

Example 103 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (133)

Following the procedure of Example 63 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (133) as a white solid.

Example 104 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (134)

Following the procedure of Example 64 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (134) as a white solid.

Example 105 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (135)

Following the procedure of Example 65 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (135) as a white solid.

Example 106 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (136)

Following the procedure of Example 66 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (136) as a white solid.

Example 107 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (137)

Following the procedure of Example 67 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (137) as a white solid.

Example 108 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (138)

Following the procedure of Example 68 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (138) as a white solid.

Example 109 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (139)

Following the procedure of Example 69 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (139) as a white solid.

Example 110 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-(2S)-fluoropropyl(cyclohexylmethyl)phosphinicAcid (140)

Following the procedure of Example 70 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-(2S)-fluoropropyl(cyclohexylmethyl)phosphinic acid affords thetitle compound (140) as a white solid.

Example 111 Synthesis of3-{[1-Isobutanoyloxyethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (141)

Following the procedure of Example 61 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (141) as a white solid.

Example 112 Synthesis of3-{[1-Butanoyloxyethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (142)

Following the procedure of Example 62 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (142) as a white solid.

Example 113 Synthesis of3-{[1-Pivaloyloxyethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (143)

Following the procedure of Example 63 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (143) as a white solid.

Example 114 Synthesis of3-{[1-Cyclohexanoyloxyethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (144)

Following the procedure of Example 64 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (144) as a white solid.

Example 115 Synthesis of3-{[Isobutanoyloxymethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (145)

Following the procedure of Example 65 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (145) as a white solid.

Example 116 Synthesis of3-{[Butanoyloxymethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (146)

Following the procedure of Example 66 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (146) as a white solid.

Example 117 Synthesis of3-{[Pivaloyloxymethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (147)

Following the procedure of Example 67 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (147) as a white solid.

Example 118 Synthesis of3-{[Cyclohexanoyloxymethoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (148)

Following the procedure of Example 68 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (148) as a white solid.

Example 119 Synthesis of3-{[(1R)-Isobutanoyloxyisobutoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (149)

Following the procedure of Example 69 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (149) as a white solid.

Example 120 Synthesis of3-{[(1S)-Isobutanoyloxyisobutoxy]carbonylamino}-2-oxopropyl(cyclohexylmethyl)phosphinicAcid (150)

Following the procedure of Example 70 and replacing3-aminopropyl(cyclohexylmethyl)phosphinic acid with3-amino-2-oxopropyl(cyclohexylmethyl)phosphinic acid affords the titlecompound (150) as a white solid.

Example 121 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (151)

To a solution of3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid (10 mmol) and sodium bicarbonate (20 mmol) in water (40 mL) isadded a solution of compound (17) (10 mmol) in acetonitrile (20 mL) over1 min. The reaction is stirred at ambient temperature for 16 h. Thereaction mixture is diluted with diethyl ether (100 mL) and washed with0.1 M aqueous potassium bisulfate (3×100 mL). The organic phase isseparated, dried over anhydrous magnesium sulfate, filtered, andconcentrated in vacuo to afford the title compound (151) as a whitesolid.

Example 122 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (152)

Following the procedure of Example 121 and replacing compound (17) withcompound (18) affords the title compound (152) as a white solid.

Example 123 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (153)

Following the procedure of Example 121 and replacing compound (17) withcompound (19) affords the title compound (153) as a white solid.

Example 124 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (154)

Following the procedure of Example 121 and replacing compound (17) withcompound (20) affords the title compound (154) as a white solid.

Example 125 Synthesis of3-{N-(Isobutanoyloxymethoxy]carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (155)

Following the procedure of Example 121 and replacing compound (17) withcompound (21) affords the title compound (155) as a white solid.

Example 126 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (156)

Following the procedure of Example 121 and replacing compound (17) withcompound (22) affords the title compound (156) as a white solid.

Example 127 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (157)

Following the procedure of Example 121 and replacing compound (17) withcompound (23) affords the title compound (157) as a white solid.

Example 128 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (158)

Following the procedure of Example 121 and replacing compound (17) withcompound (24) affords the title compound (158) as a white solid.

Example 129 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (159)

To a 3 L three necked round bottom flask fitted with a mechanicalstirrer, temperature probe, and nitrogen inlet is added compound (25)(100 mmol),3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid (100 mmol), THF (1 L), and water (100 mL). The suspension isstirred under a nitrogen atmosphere at 18-20° C. for 4 h during whichtime the reaction mixture becomes homogeneous. The THF is removed invacuo and the reaction mixture is diluted with methyl tert-butyl ether(250 mL) and washed with 1N HCl (1×500 mL) and water (2×200 mL). Theorganic phase is separated and concentrated in vacuo to leave a whitesolid. The solid is purified by flash chromatography to afford theproduct (159) as a white solid.

Example 130 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (160)

Following the procedure of Example 129 and replacing compound (25) withcompound (28) affords the title compound (160) as a white solid.

Example 131 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (161)

Following the procedure of Example 121 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (161) as a white solid.

Example 132 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (162)

Following the procedure of Example 122 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (162) as a white solid.

Example 133 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (163)

Following the procedure of Example 123 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (163) as a white solid.

Example 134 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (164)

Following the procedure of Example 124 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (164) as a white solid.

Example 135 Synthesis of3-{N-(Isobutanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (165)

Following the procedure of Example 125 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (165) as a white solid.

Example 136 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (166)

Following the procedure of Example 126 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (166) as a white solid.

Example 137 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (167)

Following the procedure of Example 127 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (167) as a white solid.

Example 138 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (168)

Following the procedure of Example 128 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (168) as a white solid.

Example 139 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (169)

Following the procedure of Example 129 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (169) as a white solid.

Example 140 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (170)

Following the procedure of Example 130 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (170) as a white solid.

Example 141 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (171)

Following the procedure of Example 121 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (171) as a white solid.

Example 142 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (172)

Following the procedure of Example 122 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (172) as a white solid.

Example 143 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (173)

Following the procedure of Example 123 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (173) as a white solid.

Example 144 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (174)

Following the procedure of Example 124 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (174) as a white solid.

Example 145 Synthesis of3-{N-(Isobutanoyloxymethoxy]carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (175)

Following the procedure of Example 125 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (175) as a white solid.

Example 146 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (176)

Following the procedure of Example 126 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (176) as a white solid.

Example 147 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (177)

Following the procedure of Example 127 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (177) as a white solid.

Example 148 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (178)

Following the procedure of Example 128 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (178) as a white solid.

Example 149 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (179)

Following the procedure of Example 129 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with 3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (179) as a white solid.

Example 150 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (180)

Following the procedure of Example 130 and replacing3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(R)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (180) as a white solid.

Example 151 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (181)

To a solution of3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid (10 mmol) and sodium bicarbonate (20 mmol) in water (40 mL) isadded a solution of compound (17) (10 mmol) in acetonitrile (20 mL) over1 min. The reaction is stirred at ambient temperature for 16 h. Thereaction mixture is diluted with diethyl ether (100 mL) and washed with0.1 M aqueous potassium bisulfate (3×100 mL). The organic phase isseparated, dried over anhydrous magnesium sulfate, filtered, andconcentrated in vacuo to afford the title compound (181) as a whitesolid.

Example 152 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (182)

Following the procedure of Example 151 and replacing compound (17) withcompound (18) affords the title compound (182) as a white solid.

Example 153 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (183)

Following the procedure of Example 151 and replacing compound (17) withcompound (19) affords the title compound (183) as a white solid.

Example 154 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (184)

Following the procedure of Example 151 and replacing compound (17) withcompound (20) affords the title compound (184) as a white solid.

Example 155 Synthesis of3-{N-(Isobutanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (185)

Following the procedure of Example 151 and replacing compound (17) withcompound (21) affords the title compound (185) as a white solid.

Example 156 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (186)

Following the procedure of Example 151 and replacing compound (17) withcompound (22) affords the title compound (186) as a white solid.

Example 157 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (187)

Following the procedure of Example 151 and replacing compound (17) withcompound (23) affords the title compound (187) as a white solid.

Example 158 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (188)

Following the procedure of Example 151 and replacing compound (17) withcompound (24) affords the title compound (188) as a white solid.

Example 159 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (189)

To a 3 L three necked round bottom flask fitted with a mechanicalstirrer, temperature probe, and nitrogen inlet is added compound (25)(100 mmol),3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid (100 mmol), THF (1 L), and water (100 mL). The suspension isstirred under a nitrogen atmosphere at 18-20° C. for 4 h during whichtime the reaction mixture becomes homogeneous. The THF is removed invacuo and the reaction mixture is diluted with methyl tert-butyl ether(250 mL) and washed with 1N HCl (1×500 mL) and water (2×200 mL). Theorganic phase is separated and concentrated in vacuo to leave a whitesolid. The solid is purified by flash chromatography to afford theproduct (189) as a white solid.

Example 160 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}propyl(cyclohexylmethyl)phosphinicAcid (190)

Following the procedure of Example 159 and replacing compound (25) withcompound (28) affords the title compound (190) as a white solid.

Example 161 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (191)

Following the procedure of Example 151 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (191) as a white solid.

Example 162 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (192)

Following the procedure of Example 152 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (192) as a white solid.

Example 163 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (193)

Following the procedure of Example 153 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (193) as a white solid.

Example 164 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (194)

Following the procedure of Example 154 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (194) as a white solid.

Example 165 Synthesis of3-{N-(Isobutanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (195)

Following the procedure of Example 155 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (195) as a white solid.

Example 166 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (196)

Following the procedure of Example 156 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (196) as a white solid.

Example 167 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (197)

Following the procedure of Example 157 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (197) as a white solid.

Example 168 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (198)

Following the procedure of Example 158 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (198) as a white solid.

Example 169 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (199)

Following the procedure of Example 159 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (199) as a white solid.

Example 170 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (200)

Following the procedure of Example 160 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(s)-(3,4-dichlorophenyl)ethyl]amino}-(2R)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (200) as a white solid.

Example 171 Synthesis of3-{N-(1′-Isobutanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (201)

Following the procedure of Example 151 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (201) as a white solid.

Example 172 Synthesis of3-{N-(1′-Butanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (202)

Following the procedure of Example 152 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (202) as a white solid.

Example 173 Synthesis of3-{N-(1′-Pivaloyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (203)

Following the procedure of Example 153 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (203) as a white solid.

Example 174 Synthesis of3-{N-(1′-Cyclohexanoyloxyethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (204)

Following the procedure of Example 154 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (204) as a white solid.

Example 175 Synthesis of3-{N-(Isobutanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (205)

Following the procedure of Example 155 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (205) as a white solid.

Example 176 Synthesis of3-{N-(Butanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (206)

Following the procedure of Example 156 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (206) as a white solid.

Example 177 Synthesis of3-{N-(Pivaloyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (207)

Following the procedure of Example 157 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (207) as a white solid.

Example 178 Synthesis of3-{N-(Cyclohexanoyloxymethoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (208)

Following the procedure of Example 158 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (208) as a white solid.

Example 179 Synthesis of3-{N-((1′R)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (209)

Following the procedure of Example 159 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (209) as a white solid.

Example 180 Synthesis of3-{N-((1′S)-Isobutanoyloxyisobutoxy)carbonyl-N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicAcid (210)

Following the procedure of Example 160 and replacing3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-propyl(cyclohexylmethyl)phosphinicacid with3-{N-[1(S)-(3,4-dichlorophenyl)ethyl]amino}-(2S)-hydroxypropyl(cyclohexylmethyl)phosphinicacid affords the title compound (210) as a white solid.

Example 181 Synthesis of3-{[1-Benzoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(211)

Following the procedure of Example 1 and replacing compound (17) withcompound (214) afforded the title compound (211) as a white solid.¹H-NMR (400 MHz, CDCl₃): δ 8.03 (d, J=8 Hz, 2H), 7.53 (t, J=8.8 Hz, 1H),7.41 (t, J=8 Hz, 2H), 7.06 (q, J=5.2 Hz, 1H), 3.48 (s, 1H), 3.25-3.28(m, 2H), 1.53-1.81 (m, 10H), 1.36-1.41 (m, 2H), 0.9 (t, J=7.2 Hz, 3H).Phosphorus (162 MHz, CD₃OD) δ0.33. MS (ESI) m/z 372 (M+H)⁺.

Example 182 Synthesis of3-{[1-Benzoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinic Acid(212)

Following the procedure of Example 1 and replacing compound (17) withcompound (216) afforded the title compound (212) as a white solid.¹H-NMR (400 MHz, CDCl₃): δ 8.03 (dd, J=1.6 Hz, 1.6 Hz, 2H), 7.55 (t,J=7.2 Hz, 1H), 7.41 (t, J=8 Hz, 2H), 5.95 (s, 2H), 3.28 (t, J=6.8 Hz,2H), 1.80-1.84 (m, 2H), 1.61-1.74 (m, 4H 0, 1.51-1.53 (m, 2H), 1.34-1.39(m, 2H), 0.88 (t, J=7.2 Hz, 3H). Phosphorus (162 MHz, CD₃OD) δ9.50. MS(ESI) m/z 358 (M+H)⁺.

Example 183 Synthesis of3-{(Isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinic AcidSodium Salt (213)

Compound 39 was dissolved in a mixture of water and acetonitrile, anaqueous solution of 1 eq. NaHCO₃ was added, the mixture stirred forabout 10 min, and lyophilized to afford the title compound (213). ¹H-NMR(400 MHz, CDCl₃): δ 6.55 (d, J=4.8 Hz, 1H), 3.10 (t, J=6.4 Hz, 2H),2.53-2.56 (m, 1H), 1.97-2.00 (m, 1H), 1.79-1.83 (m, 2H), 1.70-1.74 (m,2H), 1.53-1.58 (m, 2H), 1.37-1.43 (m, 2H), 1.15 (t, J=6.8 Hz, 6H), 0.90(t, J=7.2 Hz, 9H). Phosphorus (162 MHz, CD₃OD) δ0.36; MS (ESI) m/z 366(M+H)⁺.

Example 184 Synthesis of3-{(Butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic AcidSodium Salt (214)

Following the procedure of Example 1 and replacing compound (17) withcompound (18) afforded3-{[1-butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid.3-{[1-Butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid wasdissolved in a mixture of water and acetonitrile, an aqueous solution of1 eq. NaHCO₃ was added, the mixture stirred for about 10 min, andlyophilized to afford the title compound (214). ¹H-NMR (400 MHz, CD₃OD):δ 6.75-6.71 (q, J=5.6, 16.4 Hz, 1H), 3.15-3.08 (m, 2H), 2.29-2.25 (d,J=1.6 Hz, 2H), 1.73-1.35 (m, 16H), 0.95-0.90 (q, J=7.6 Hz, 3H).Phosphorus (162 MHz, CD₃OD): 42.747; MS (ESI) m/z 337 (M+H)⁺.

Example 185 Methods for Determination of Enzmmatic Cleavage of Prodrugsin Vitro

The stabilities of prodrugs were evaluated in one or more in vitrosystems using a variety of tissue preparations following methods knownin the art. The chemical stability of prodrugs in aqueous buffers at apH of 2.0, 7.4, and 8.0 were also measured. Tissues were obtained fromcommercial sources (e.g., Pel-Freez Biologicals, Rogers, Ark., orGenTest Corporation, Woburn, Mass.). Experimental conditions used forthe in vitro studies are described in Table 1. Each preparation wasincubated with test compound at 37° C. for one hour. Aliquots (50 μL)were removed at 0, 30, and 60 min and quenched with 0.1% trifluoroaceticacid in acetonitrile. Samples were then centrifuged and analyzed byLC/MS/MS. Stability of prodrugs towards specific enzymes (e.g.,peptidases, etc.) was also assessed in vitro by incubation with thepurified enzyme.

Pancreatin Stability: Stability studies were conducted by incubatingprodrug (5 μM) with 1% (w/v) pancreatin (Sigma, P-1625, from porcinepancreas) in 0.025 M Tris buffer containing 0.5 M NaCl (pH 7.5) at 37°C. for 60 min. The reaction was stopped by addition of 2 volumes ofmethanol. After centrifugation at 14,000 rpm for 10 min, the supernatantwas removed and analyzed by LC/MS/MS.

Caco-2 Homogenate S9 Stability: Caco-2 cells were grown for 21 daysprior to harvesting. Culture medium was removed and cell monolayers wererinsed and scraped off into ice-cold 10 mM sodium phosphate/0.15 Mpotassium chloride, pH 7.4. Cells were lysed by sonication at 4° C.using a probe sonicator. Lysed cells were then transferred into 1.5 mLcentrifuge vials and centrifuged at 9,000 g for 20 min at 4° C. Theresulting supernatant (Caco-2 cell homogenate S9 fraction) was aliquotedinto 0.5 mL vials and stored at −80° C. until used.

TABLE 1 Conditions for Prodrug In Vitro Metabolism Studies SubstratePreparation Concentration Cofactors Rat Plasma 2.0 μM None Human Plasma2.0 μM None Rat Liver S9 2.0 μM NADPH* (0.5 mg/mL) Human Liver S9 2.0 μMNADPH* (0.5 mg/mL) Human Intestine S9 2.0 μM NADPH* (0.5 mg/mL)CarboxypeptidaseA 2.0 μM None (10 units/mL) Caco-2 Homogenate 5.0 μMNone Pancreatin 5.0 μM None *NADPH generating system, e.g., 1.3 mMNADP⁺, 3.3 mM glucose-6-phosphate, 0.4 U/mL glucose-6-phosphatedehydrogenase, 3.3 mM magnesium chloride and 0.95 mg/mL potassiumphosphate, pH 7.4.

For stability studies, prodrug (5 μM) was incubated in Caco-2 homogenateS9 fraction (0.5 mg protein per mL) for 60 min at 37° C. Concentrationsof intact prodrug and released tranexamic acid were determined at zerotime and 60 min using LC/MS/MS.

pH-Dependent Stability: The long-term pH-dependent stability oftranexamic acid prodrug at 37° C. was measured by LC/MS/MS at fivedifferent representative pH values from pH 2.0 to pH 8.0 was determined.The test concentration was 5 μM. The amount of remaining prodrug and theamount of tranexamic acid released from the prodrug was determined at 0hour and after 24 hours.

Compounds 31, 35, 39/40, 211, and 212, for example, showed goodstability from pH 2 to pH 8, and are hydrolyzed to release thecorresponding 3-aminopropylphosphinic acid analogs in the presence ofthe tissue preparations.

Example 186 In Vitro Determination of Caco-2 Cellular Permeability ofProdrugs

The passive permeability of the prodrugs of the present disclosure canbe assessed in vitro using standard methods well known in the art (See,e.g., Stewart, et al., Pharm. Res., 1995, 12, 693). For example, passivepermeability can be evaluated by examining the flux of a prodrug acrossa cultured polarized cell monolayer (e.g., Caco-2 cells).

Caco-2 cells are obtained from continuous culture (passage less than 28)were seeded at high density onto Transwell polycarbonate filters. Cellsare maintained with DMEM/10% fetal bovine serum, 1 mM nonessential aminoacids, and 6 mM L-Gln, 5% CO₂/95% O₂, at 37° C. until the day of theexperiment. Permeability studies are conducted at pH 6.5 apically (in 50mM MES buffer containing 1 mM CaCl₂, 1 mM MgCl₂, 150 mM NaCl, 3 mM KCl,1 mM NaH₂PO₄, 5 mM glucose) and pH 7.4 basolaterally (in Hanks' balancedsalt solution containing 10 mM HEPES) in the presence of efflux pumpinhibitors (250 μM MK-571 and 250 μM Verapamil). Inserts are placed in12 or 24 well plates containing buffer and incubated for 30 min at 37°C. Prodrug (200 μM) is added to the apical or basolateral compartment(donor) and concentrations of prodrug and/or released parent drug in theopposite compartment (receiver) are determined at intervals over 1 hourusing LC/MS/MS. Values of apparent permeability (P_(app)) are calculatedusing the equation:

P _(app) =V _(r)(dC/dt)//(AC _(o))

where V_(r) is the volume of the receiver compartment in mL; dC/dt isthe total flux of prodrug and parent drug (μM/sec), determined from theslope of the plot of concentration in the receiver compartment versustime; C₀ is the initial concentration of prodrug in μM; and A is thesurface area of the membrane in cm². Prodrugs with significanttranscellular permeability can exhibit a value of P_(app) of ≧1×10⁻⁶, avalue of P_(app) of ≧1×10⁻⁵ cm/sec, or a value of P_(app) of ≧5×10⁻⁵cm/sec. Prodrugs having a high P_(app) should be well absorbed from theintestine. Prodrugs for which the apical-to-basolateral permeabilitiesexceeds their basolateral-to-apical permeability may be substrates foractive transport mechanisms present in the apical membrane of Caco-2cells (although some component of this transcellular permeability mayalso be mediated by passive diffusion).

Example 187 Bioavailability of Prodrugs and Metabolites ThereofFollowing Intracolonic Administration in Rats Step A: AdministrationProtocol

Rats are obtained commercially and are pre-cannulated in the both theascending colon and the jugular vein. Animals are conscious at the timeof the experiment. All animals are fasted overnight and until 4 hourspost-dosing of a prodrug of 3-aminopropylphosphinic or analog thereof.3-aminopropylphosphinic or analog thereof or the corresponding prodrugis administered as a solution (in water) directly into the colon via thecannula at a dose equivalent to about 75 mg or other appropriate dose ofa 3-aminopropylphosphinic or analog thereof per kg body weight. Bloodsamples (0.3 mL) are obtained from the jugular cannula at intervals over8 hours and are quenched immediately by addition of sodium metabisulfiteto prevent oxidation of the 3-aminopropylphosphinic or analog thereof.Blood is then further quenched with methanol/perchloric acid to preventhydrolysis of the prodrug. Blood samples are analyzed as described inSteps B and C.

Step B: Sample Preparation for Colonically Absorbed Drug

300 μL of methanol is added to 1.5 mL tubes. Rat blood (100 μL) iscollected at different times into the tubes and vortexed to mix. 90 μLof rat blood is quenched with 300 μL methanol. 10 μL of a standard stocksolution containing an α-amino acid (0.04, 0.2, 1, 5, 25, and 100 μg/1mL) and 20 μL of p-chlorophenylalanine is added to 90 μL of rat blood tomake up a final calibration standard (0.004, 0.02, 0.1, 0.5, 2.5, and 10μg/mL). Samples are vortexed and centrifuged at 3400 rpm for 20 min. Thesupernatant is analyzed by LC/MS/MS.

Step C: LC/MS/MS Analysis

An API 4000 LC/MS/MS spectrometer equipped with Agilent 1100 binarypumps and a CTC HTS-PAL autosampler are used in the analysis. AThermoHypersil-Keystone Betasil C18 100×4.6 mm, 5 μM column is usedduring the analysis. The mobile phase is 0.1% formic acid in water (A)and 0.1% formic acid in acetonitrile (B). The flow rate is 1.2 mL/min.The gradient condition is: 1% B for 0.5 min, then to 95% B for 1.8 min,and maintained at 95% B for 1.7 min. Then the mobile phase is returnedto 1% B for 2.5 min. A TurboIonSpray source is used on the API 4000. Theanalysis is done in either negative ion mode or positive ion mode asappropriate and the MRM transition for each analyte is optimized usingstandard solution. 20 μL of the samples are injected. Non-compartmentalanalysis is performed using WinNonlin software (v. 3.1 ProfessionalVersion, Pharsight Corporation, Mountain View, Calif.) on individualanimal profiles. Summary statistics on major parameter estimates isperformed for C_(max) (peak observed concentration following dosing),T_(max) (time to maximum concentration is the time at which the peakconcentration was observed), AUC_((0-t)) (area under the plasmaconcentration-time curve from time zero to last collection time,estimated using the log-linear trapezoidal method), AUC_((0-∞)), (areaunder the plasma concentration time curve from time zero to infinity,estimated using the log-linear trapezoidal method to the last collectiontime with extrapolation to infinity), and t_(1/2,z) (terminalhalf-life).

Prodrugs that provide a bioavailability of the corresponding3-aminopropylphosphinic or analog thereof that is greater than thebioavailability provided by an equimolar dose of the3-aminopropylphosphinic or analog thereof administered to a patient bythe same route (e.g., oral administration) can be useful as therapeuticagents, and more particularly, as sustained release therapeutic agents.

Example 188 Animal Model for Assessing Therapeutic Efficacy of Prodrugsof 3-Aminopropylphosphinic Acid Analogs for Treating Alzheimer's Disease

Heterozygous transgenic mice expressing the Swedish AD mutant gene,hAPPK670N, M671L (Tg2576; Hsiao, Learning & Memory 2001, 8, 301-308) areused as an animal model of Alzheimer's disease. Animals are housed understandard conditions with a 12:12 light/dark cycle and food and wateravailable ad libitum. Beginning at 9 months of age, mice are dividedinto two groups. The first two groups of animals receive increasingdoses of 3-aminopropylphosphinic acid analog prodrug, over six weeks.The remaining control group receives daily saline injections for sixweeks.

Behavioral testing is performed at each drug dose using the samesequence over two weeks in all experimental groups: 1) spatial reversallearning, 2) locomotion, 3) fear conditioning, and 4) shock sensitivity.This order is selected to minimize interference among testing paradigms.

Acquisition of the spatial learning paradigm and reversal learning aretested during the first five days of test compound administration usinga water T-maze as described in Bardgett et al., Brain Res Bull 2003, 60,131-142. Mice are habituated to the water T-maze during days 1-3, andtask acquisition begins on day 4. On day 4, mice are trained to find theescape platform in one choice arm of the maze until 6 to 8 correctchoices are made on consecutive trails. The reversal learning phase isthen conducted on day 5. During the reversal learning phase, mice aretrained to find the escape platform in the choice arm opposite from thelocation of the escape platform on day 4. The same performance criterionand inter-trial interval are used as during task acquisition.

Large ambulatory movements are assessed to determine that the results ofthe spatial reversal learning paradigm are not influenced by thecapacity for ambulation. After a rest period of two days, horizontalambulatory movements, excluding vertical and fine motor movements, areassessed in a chamber equipped with a grid of motion-sensitive detectorson day 8. The number of movements accompanied by simultaneous blockingand unblocking of a detector in the horizontal dimension are measuredduring a one-hour period.

The animals' capacity for contextual and cued memory is tested using afear conditioning paradigm beginning on day 9. Testing takes place in achamber that contains a piece of absorbent cotton soaked in anodor-emitting solution such as mint extract placed below the grid floor.A 5-min, 3 trial 80 db, 2800 Hz tone-foot shock sequence is administeredto train the animals on day 9. On day 10, memory for context is testedby returning each mouse to the chamber without exposure to the tone andfoot shock, and recording the presence or absence of freezing behaviorevery 10 seconds for 8 minutes. Freezing is defined as no movement, suchas ambulation, sniffing or stereotypy, other than respiration.

On day 11, the animals' response to an alternate context and to theauditory cue is tested. Coconut extract is placed in a cup and the 80 dBtone is presented, but no foot shock is delivered. The presence orabsence of freezing in response to the alternate context is thendetermined during the first 2 minutes of the trial. The tone is thenpresented continuously for the remaining 8 minutes of the trial, and thepresence or absence of freezing in response to the tone is determined.

On day 12, the animals are tested to assess their sensitivity to theconditioning stimulus, i.e., foot shock.

Following the last day of behavioral testing, animals are anesthetizedand the brains removed, post-fixed overnight, and sections cut throughthe hippocampus. The sections are stained to image β-amyloid plaques(see e.g., Dong et al., Neuroscience 2004, 127, 601-609).

Data are analyzed using appropriate statistical methods.

Example 189 Animal Model for Assessing Therapeutic Efficacy of Prodrugsof 3-Aminopropylphosphinic Acid Analogs for Treating Depression ForcedSwim Test in Rats

Male Wistar rats weighting 230-270 g are acclimated to the colony roomfor a minimum of 1 week, handled daily for at least 4 days andhabituated to saline injections for 2 days before the experiments.

Two glass cylinders (20 cm dia×40 cm height) are separated by blackopaque partitions and filled with water at about 24° C. to a depth of 30cm. At this depth a rat cannot stand on the cylinder bottom. The waterlevel is 10 cm from the top. Water is changed before each animal isplaced into the water tank. An experimental session consists of twotrials. During the conditioning trial, rats are gently placed into thecylinders for 15 min. After the trial, rats are dried and placed into awarm cage with the paper towels for 10-15 min before being returned totheir home cages. Twenty-four hours later, for the test trial, animalsare placed again into the cylinders for a 5-min test session. Tests arevideo taped for subsequent quantitative behavioral analysis. Thefrequency and/or total duration are calculated for each of the followingcategories: passive/immobile behavior (floating is scored when an animalremains in the water with all four limbs motionless, except foroccasional alternate movements of paws and tail necessary to preventsinking and to keep head/nose above the water); active/mobile behaviors(swimming characterized by rigorous movements with all four legs;paddling characterized by floating with rhythmical simultaneous kicksand occasional pushes off the wall to give speed and direction to thedrift), including escape-oriented behaviors (climbing characterized byintense movements with all four limbs, with the two forepaws breakingthe surface of the water and being directed against the walls of thecylinder; diving characterized by movements towards the bottom of thecylinder with the rat's head below its hind limbs), and self-directedbehaviors (headshakes, vigorous headshakes to get water off the snoutand eyes; wiping, rubbing water away from the snout). In addition, atthe end of each test trial, fecal boli are counted. A test compound,control, or positive control (e.g., imipramine) is administered prior tothe test.

Tail Suspension Test in Mice

Mice are housed in standard laboratory cages and acclimated. Mice aremoved from the housing room to the testing area in their home cages andallowed to adapt to the new environment for at least 1 h before testing.Immobility is induced by tail suspension according to the procedure ofSteru et al., Psychopharmacology 1985, 85, 367-370. Mice are lyingindividually on a paper adhesive tape, 65 cm above a tabletop. Tape isplaced approximately 1 cm from the tip of the tail. Animals are allowedto hang for 6 min and the duration of immobility is recorded. Mice areconsidered immobile only when hanging passively and completelymotionless. Mice from these experiments are used one week later inlocomotor activity studies. A test compound, control, or positivecontrol (e.g., imipramine) is administered prior to the test.

Locomotor Activity

The spontaneous locomotor activity of mice is measured in photoresistoractometers (circular cages, 25 cm in dia, 15 cm high, two light sources,two photoresistors), wherein the animals are placed individually 1 hafter injection of a test compound. The number of crossings of lightbeams is measured during the first 30 min of the experimental session.The first measurement is performed 6 min after placing an animal intothe actometer.

The spontaneous locomotor activity of rats is measured in photoresistoractometers (40×40×25 cm, two light sources, two photoresistors), wherethe animals are placed after administration of a test compound. Thenumber of crossings of light beams is measured during the first 30 minof an experimental session. The first measurement is performed 5 minafter placing an animal in the actometer.

Example 190 Animal Model for Assessing Therapeutic Efficacy of Prodrugsof 3-Aminopropylphosphinic Acid Analogs for Treating Anxiety

A method for assessing the effects of test compounds on anxietydescribed by Pellow and File, Pharmacol Biochem Behav 1986, 24, 524-529,i.e., the elevated plus-maze test, is used. A plus-maze is consists oftwo open arms (50×10 cm) and two closed arms (50×10×40 cm). The armsextend from a central platform (10×10 cm) and are raised 50 cm. Eachmouse is placed at the center of the maze facing a closed arm and isallowed to explore the maze for 5 min. The time spent in the open armsand the time spent in the closed arms is monitored, and the percent oftime spent in the open arms determined. Increased time spent in the openarms indicates an anxiolytic effect for the test condition. A test thatmeasures spontaneous locomotor activity such as measurement in anactivity cage can be used to determine whether the test compound alsoaffects locomotor activity. It is desirable that a compound exhibitingan anxiolytic effect not decrease locomotor activity.

Example 191 Animal Model for Assessing Therapeutic Efficacy of Prodrugsof 3-Aminopropylphosphinic Acid Analogs for Treating Epilepsy El MouseModel

The “epilepsy” (El) mouse model to monitor seizure susceptibility afteradministration of a prodrug of 3-aminopropylphosphinic acid analog(Murashima et al., Epilepsia 2002, 43(Suppl. 5), 130-135).

Seizure susceptible El mice are at least 6 months old at the time oftesting. Seizure phenotype in response to tail suspension handlingduring routine husbandry is recorded for each cage of El mice afterweaning in order to match treatment groups.

One experimental trial is completed over a 3 day period and three trialsare completed over a 7 day period. On day 1 of each trial, all mice areweighed and singly housed in weight matched groups. Each mouse isprovided with a pre-weighed food container with a chow or a testcompound wet mash ration at the beginning of each 24 h period. Onsubsequent days, the food containers are removed, weighed and thenrefilled with fresh food. Mice in a yoked condition are fed the averageamount of food consumed by the test compound group over the previous 24h period. This procedure assures that non-appetitive actions of the testcompound are responsible for anticonvulsion efficacy.

On the final day of diet exposure, a seizure susceptibility test isperformed in which mice are picked up by their tails and held 10-20 cmabove the floor of their home cage for 30 s. Mice are then placed in aclean cage for 2 min and then lifted by the tail for another 15 s beforebeing returned to their home cage. Behavioral characteristics ofseizures in El mice are evident during three specific phases: (1)prodromal: squeaking and transient immobility, followed by “runningfits;” (2) ictal: convulsions starting with the hind limbs but rapidlybecoming generalized tonic-clonic, loss of postural equilibrium, tailcocked over head (Straub tail), salivation, defecation, and urination;and (3) post-ictal: lethargy, “kangaroo posture” (sitting on hind legswith forepaws drawn up), turning of the head in alternate directions,and occasional hyperirritability. Seizures are determined to haveoccurred in mice that exhibited behavioral signs such as squeaking,tonic-clonic jerking, cocked tail over the head, loss of posture andpost-ictal ataxia. Seizure activity can be quantified using anall-or-none criterion or by scoring seizure severity.

Pilocarpine Epilepsy Model

Young adult male Wistar-2 rats (210-270 kg; 35-42 days) are injectedwith pilocarpine (340 mg/kg, i.p.) 30 min after injection ofmethylscopolamine (1 mg/kg, i.p.) (Kudin et al., Eur J Neurosci 2002,15, 1105-14). Seizure activity begins 20 to 40 min after pilocarpineadministration. After 40 min of status epilepticus (SE), the rats areinjected with diazepam (DZP; 4 mg/kg, i.p.) or test compound. In thetest compound group(s), the SE is terminated after 120 min by DZP (4mg/kg, i.p.). Control rats receive methylscopolamine, test compound,DZP, or physiologic salt solution instead of pilocarpine.

To determine the seizure frequency, the behavior of the rats ismonitored by video (125 h total time). Monitoring begins 14 days afterpilocarpine injection using the following protocol. At day 14 afterpilocarpine injection, rats are monitored for a total of 5 h, and on thefollowing 12 days, 10 h per day (during the daytime only). Scoring ofbehavioral seizures is done according to Cavalheiro et al., Epilepsia1991, 32, 778-82, applying the kindling stages defined by Racine,Electroencephalogr Clin Neurophysiol 1972, 32, 281-94. Referring to this5-point rating scale, clearly detectable motor seizures (rearing/stage1V or rearing and falling/stage V) are counted.

Finally, it should be noted that there are alternative ways ofimplementing the present disclosure. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive,and the invention is not to be limited to the details given herein, butmay be modified within the scope and equivalents of the claims issuinghere from.

1. A compound of Formula (I):

a pharmaceutically acceptable salt thereof, and a pharmaceuticallyacceptable solvate of any of the foregoing, wherein: R¹ is chosen fromacyl, substituted acyl, alkyl, substituted alkyl, aryl, substitutedaryl, arylalkyl, substituted arylalkyl, cycloalkyl, substitutedcycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl,substituted heteroalkyl, heteroaryl, substituted heteroaryl,heteroarylalkyl, and substituted heteroarylalkyl; R² and R³ is chosenfrom hydrogen, alkyl, substituted alkyl, alkoxycarbonyl, substitutedalkoxycarbonyl, aryl, substituted aryl, arylalkyl, substitutedarylalkyl, cycloalkyl, substituted cycloalkyl, heteroaryl, substitutedheteroaryl, heteroarylalkyl, and substituted heteroarylalkyl; or R² andR³ together with the carbon atom to which they are bonded form acycloalkyl, substituted cycloalkyl, cycloheteroalkyl, or substitutedcycloheteroalkyl ring; R⁴ is chosen from C₂₋₆ alkyl, substituted C₂₋₆alkyl, benzyl, substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇cycloalkylmethyl, and dialkoxymethyl; R⁵ is chosen from hydrogen,hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl, substituted C₁₋₄ alkyl,aryl, substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl; R⁶ and R⁷ is chosen from hydrogen, C₁₋₆ alkyl, C₁₋₆alkoxy, aryl, substituted aryl, C₃₋₆ cycloalkyl, heteroaryl, substitutedheteroaryl, C₇₋₉ phenylalkyl, and substituted C₇₋₉ phenylalkyl; and R⁸is chosen from hydrogen, C₁₋₆ alkyl, substituted C₁₋₆ alkyl, aryl,substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl.
 2. The compound of claim 1, wherein R¹ is chosen frommethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-dimethoxyethyl, 1,1-diethoxyethyl, phenyl, 4-methoxyphenyl, benzyl,phenethyl, styryl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl,2-pyridyl, 3-pyridyl, and 4-pyridyl.
 3. The compound of claim 1, whereinR¹ is chosen from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,1,1-diethoxyethyl, phenyl, cyclohexyl, and 3-pyridyl.
 4. The compound ofclaim 1, wherein R¹ is chosen from propyl, isopropyl, tert-butyl,cyclohexyl, and phenyl.
 5. The compound of claim 1, wherein R² is chosenfrom hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, phenyl, and cyclohexyl, and R³ is hydrogen. 6.The compound of claim 1, wherein R² is chosen from hydrogen, methyl, andisopropyl; and R³ is hydrogen.
 7. The compound of claim 1, wherein R³ ishydrogen.
 8. The compound of claim 1, wherein R⁴ is chosen from ethyl,n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,isopentyl, sec-pentyl, neopentyl, n-hexyl, n-heptyl, allyl,2-methylallyl, but-3-enyl, propargyl, but-2-ynyl, but-3-ynyl,pent-3-ynyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl,cyclopentylmethyl, cyclohexylmethyl, cycloheptylmethyl, 2-methoxyethyl,3-methoxypropyl, 3-ethoxypropyl, 1-hydroxyethyl, 1-hydroxybutyl,1-hydroxyisobutyl, benzyl, 1-hydroxybenzyl, and diethoxymethyl.
 9. Thecompound of claim 1, wherein R⁴ is chosen from ethyl, n-propyl, n-butyl,diethoxymethyl, cyclohexylmethyl, and benzyl.
 10. The compound of claim1, wherein R⁴ is n-butyl.
 11. The compound of claim 1, wherein R⁵ ischosen from hydrogen, hydroxy, fluoro, oxo, and 4-chlorophenyl.
 12. Thecompound of claim 1, wherein R⁵ is chosen from hydrogen and hydroxy. 13.The compound of claim 1, wherein each of R⁶, R⁷, and R⁸ is hydrogen. 14.The compound of claim 1, wherein each of R⁶ and R⁷ is hydrogen, and R⁸is chosen from 3,5-dichlorobenzyl, 1-(3-chlorophenyl)ethyl,1-(3,4-dichlorophenyl)ethyl, 1-(3-chloro-4-iodophenyl)ethyl,1-(4-chloro-3-iodophenyl)ethyl, 3,4-dimethylbenzyl,1-(2,4-dimethoxyphenyl)ethyl, 1-(2,5-dimethoxyphenyl)ethyl,1-(2,6-dimethoxyphenyl)ethyl, 1-(3,4-dimethoxyphenyl)ethyl,1-(3,5-dimethoxyphenyl)ethyl, 1-(3,4,5-trimethoxyphenyl)ethyl,3-carboxybenzyl, 3-cyanobenzyl, 4-carboxybenzyl, 4-cyanobenzyl,1-(3-carboxyphenyl)ethyl, 1-(3-cyanophenyl)ethyl,1-(4-carboxyphenyl)ethyl, 1-(4-cyanophenyl)ethyl, 3-phenylprop-2-yl,2-(3,4-dichlorophenyl)propyl, 3-(3,4-dichlorophenyl)prop-2-yl, and3-phenyl-3-hydroxyprop-2-yl.
 15. The compound of claim 1, wherein eachof R⁶ and R⁷ is hydrogen, and R⁸ is chosen from1-(3,4-dichlorophenyl)ethyl, 1-(3-carboxyphenyl)ethyl,1-(4-carboxyphenyl)ethyl, 3,5-dichlorobenzyl, 3-carboxybenzyl, and4-carboxybenzyl.
 16. The compound of claim 1, wherein R¹ is chosen frompropyl, isopropyl, tert-butyl, cyclohexyl, and phenyl; R² is chosen fromhydrogen, methyl, and isopropyl; R⁴ is n-butyl; and each of R³, R⁵, R⁶,R⁷, and R⁸ is hydrogen.
 17. The compound of claim 1, wherein thecompound is chosen from:3-{[1-isobutanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid;3-{[benzoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acid;3-{[1-isobutanoyloxymethoxy]carbonylamino}propyl(n-butyl)phosphinicacid; 3-{[benzoyloxymethoxycarbonylamino}propyl(n-butyl)phosphinic acid;3-{[1-isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinicacid;3-{[1-cyclohexanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinicacid;3-{[1-isobutanoyloxyisobutoxy]carbonylamino}propyl(n-butyl)phosphinicacid sodium salt;3-{[butanoyloxyethoxy]carbonylamino}propyl(n-butyl)phosphinic acidsodium salt; and a pharmaceutically acceptable solvate of any of theforegoing.
 18. A pharmaceutical composition comprising a therapeuticallyeffective amount of at least one pharmaceutically acceptable vehicle andat least one compound of Formula (I):

a pharmaceutically acceptable salt thereof, and a pharmaceuticallyacceptable solvate of any of the foregoing, wherein: R¹ is chosen fromacyl, substituted acyl, alkyl, substituted alkyl, aryl, substitutedaryl, arylalkyl, substituted arylalkyl, cycloalkyl, substitutedcycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl,substituted heteroalkyl, heteroaryl, substituted heteroaryl,heteroarylalkyl, and substituted heteroarylalkyl; R² and R³ is chosenfrom hydrogen, alkyl, substituted alkyl, alkoxycarbonyl, substitutedalkoxycarbonyl, aryl, substituted aryl, arylalkyl, substitutedarylalkyl, cycloalkyl, substituted cycloalkyl, heteroaryl, substitutedheteroaryl, heteroarylalkyl, and substituted heteroarylalkyl, or R² andR³ together with the carbon atom to which they are bonded form acycloalkyl, substituted cycloalkyl, cycloheteroalkyl, or substitutedcycloheteroalkyl ring; R⁴ is chosen from C₂₋₆ alkyl, substituted C₂₋₆alkyl, benzyl, substituted benzyl, C₄₋₇ cycloalkyl, C₃₋₇cycloalkylmethyl, and dialkoxymethyl; R⁵ is chosen from hydrogen,hydroxy, mercapto, fluoro, oxo, C₁₋₄ alkyl, substituted C₁₋₄ alkyl,aryl, substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl; R⁶ and R⁷ is chosen from hydrogen, C₁₋₆ alkyl, C₁₋₆alkoxy, aryl, substituted aryl, C₃₋₆ cycloalkyl, heteroaryl, substitutedheteroaryl, C₇₋₉ phenylalkyl, and substituted C₇₋₉ phenylalkyl; and R⁸is chosen from hydrogen, C₁₋₆ alkyl, substituted C₁₋₆ alkyl, aryl,substituted aryl, C₃₋₆ cycloalkyl, substituted C₃₋₆ cycloalkyl,heteroaryl, substituted heteroaryl, C₇₋₉ phenylalkyl, and substitutedC₇₋₉ phenylalkyl.
 19. The pharmaceutical composition of claim 18,wherein the therapeutically effective amount is effective for treating adisease chosen from mild cognitive impairment, cognitive impairmentassociated with Alzheimer's disease, depression, anxiety, and epilepsy.20. The pharmaceutical composition of claim 18, wherein thepharmaceutical composition is a sustained release oral formulation. 21.A method of treating a disease in a patient comprising administering toa patient in need of such treatment the pharmaceutical composition ofclaim
 18. 22. The method of claim 21, wherein the disease is chosen froma mild cognitive impairment, cognitive impairment associated withAlzheimer's disease, depression, anxiety, and epilepsy.
 23. The methodof claim 21, wherein a therapeutically effective concentration of thecorresponding 3-aminopropylphosphinic acid analog is maintained in theplasma of the patient for at least about 4 hours after thepharmaceutical composition is orally administered to the patient.